package scipy

Get an attribute of this module as a Py.Object.t. This is useful to pass a Python function to another function.

Return the maximum of an array or maximum along an axis.

Parameters ---------- a : array_like Input data. axis : None or int or tuple of ints, optional Axis or axes along which to operate. By default, flattened input is used.

.. versionadded:: 1.7.0

If this is a tuple of ints, the maximum is selected over multiple axes, instead of a single axis or all the axes as before. out : ndarray, optional Alternative output array in which to place the result. Must be of the same shape and buffer length as the expected output. See `ufuncs-output-type` for more details.

keepdims : bool, optional If this is set to True, the axes which are reduced are left in the result as dimensions with size one. With this option, the result will broadcast correctly against the input array.

If the default value is passed, then `keepdims` will not be passed through to the `amax` method of sub-classes of `ndarray`, however any non-default value will be. If the sub-class' method does not implement `keepdims` any exceptions will be raised.

initial : scalar, optional The minimum value of an output element. Must be present to allow computation on empty slice. See `~numpy.ufunc.reduce` for details.

.. versionadded:: 1.15.0

where : array_like of bool, optional Elements to compare for the maximum. See `~numpy.ufunc.reduce` for details.

.. versionadded:: 1.17.0

Returns ------- amax : ndarray or scalar Maximum of `a`. If `axis` is None, the result is a scalar value. If `axis` is given, the result is an array of dimension ``a.ndim - 1``.

See Also -------- amin : The minimum value of an array along a given axis, propagating any NaNs. nanmax : The maximum value of an array along a given axis, ignoring any NaNs. maximum : Element-wise maximum of two arrays, propagating any NaNs. fmax : Element-wise maximum of two arrays, ignoring any NaNs. argmax : Return the indices of the maximum values.

nanmin, minimum, fmin

Notes ----- NaN values are propagated, that is if at least one item is NaN, the corresponding max value will be NaN as well. To ignore NaN values (MATLAB behavior), please use nanmax.

Don't use `amax` for element-wise comparison of 2 arrays; when ``a.shape0`` is 2, ``maximum(a0, a1)`` is faster than ``amax(a, axis=0)``.

Examples -------- >>> a = np.arange(4).reshape((2,2)) >>> a array([0, 1], [2, 3]) >>> np.amax(a) # Maximum of the flattened array 3 >>> np.amax(a, axis=0) # Maxima along the first axis array(2, 3) >>> np.amax(a, axis=1) # Maxima along the second axis array(1, 3) >>> np.amax(a, where=False, True, initial=-1, axis=0) array(-1, 3) >>> b = np.arange(5, dtype=float) >>> b2 = np.NaN >>> np.amax(b) nan >>> np.amax(b, where=~np.isnan(b), initial=-1) 4.0 >>> np.nanmax(b) 4.0

You can use an initial value to compute the maximum of an empty slice, or to initialize it to a different value:

>>> np.max([-50], [10], axis=-1, initial=0) array( 0, 10)

Notice that the initial value is used as one of the elements for which the maximum is determined, unlike for the default argument Python's max function, which is only used for empty iterables.

>>> np.max(5, initial=6) 6 >>> max(5, default=6) 5

Return the minimum of an array or minimum along an axis.

Parameters ---------- a : array_like Input data. axis : None or int or tuple of ints, optional Axis or axes along which to operate. By default, flattened input is used.

.. versionadded:: 1.7.0

If this is a tuple of ints, the minimum is selected over multiple axes, instead of a single axis or all the axes as before. out : ndarray, optional Alternative output array in which to place the result. Must be of the same shape and buffer length as the expected output. See `ufuncs-output-type` for more details.

keepdims : bool, optional If this is set to True, the axes which are reduced are left in the result as dimensions with size one. With this option, the result will broadcast correctly against the input array.

If the default value is passed, then `keepdims` will not be passed through to the `amin` method of sub-classes of `ndarray`, however any non-default value will be. If the sub-class' method does not implement `keepdims` any exceptions will be raised.

initial : scalar, optional The maximum value of an output element. Must be present to allow computation on empty slice. See `~numpy.ufunc.reduce` for details.

.. versionadded:: 1.15.0

where : array_like of bool, optional Elements to compare for the minimum. See `~numpy.ufunc.reduce` for details.

.. versionadded:: 1.17.0

Returns ------- amin : ndarray or scalar Minimum of `a`. If `axis` is None, the result is a scalar value. If `axis` is given, the result is an array of dimension ``a.ndim - 1``.

See Also -------- amax : The maximum value of an array along a given axis, propagating any NaNs. nanmin : The minimum value of an array along a given axis, ignoring any NaNs. minimum : Element-wise minimum of two arrays, propagating any NaNs. fmin : Element-wise minimum of two arrays, ignoring any NaNs. argmin : Return the indices of the minimum values.

nanmax, maximum, fmax

Notes ----- NaN values are propagated, that is if at least one item is NaN, the corresponding min value will be NaN as well. To ignore NaN values (MATLAB behavior), please use nanmin.

Don't use `amin` for element-wise comparison of 2 arrays; when ``a.shape0`` is 2, ``minimum(a0, a1)`` is faster than ``amin(a, axis=0)``.

Examples -------- >>> a = np.arange(4).reshape((2,2)) >>> a array([0, 1], [2, 3]) >>> np.amin(a) # Minimum of the flattened array 0 >>> np.amin(a, axis=0) # Minima along the first axis array(0, 1) >>> np.amin(a, axis=1) # Minima along the second axis array(0, 2) >>> np.amin(a, where=False, True, initial=10, axis=0) array(10, 1)

>>> b = np.arange(5, dtype=float) >>> b2 = np.NaN >>> np.amin(b) nan >>> np.amin(b, where=~np.isnan(b), initial=10) 0.0 >>> np.nanmin(b) 0.0

>>> np.min([-50], [10], axis=-1, initial=0) array(-50, 0)

Notice that the initial value is used as one of the elements for which the minimum is determined, unlike for the default argument Python's max function, which is only used for empty iterables.

Notice that this isn't the same as Python's ``default`` argument.

>>> np.min(6, initial=5) 5 >>> min(6, default=5) 6

Anderson-Darling test for data coming from a particular distribution.

The Anderson-Darling tests the null hypothesis that a sample is drawn from a population that follows a particular distribution. For the Anderson-Darling test, the critical values depend on which distribution is being tested against. This function works for normal, exponential, logistic, or Gumbel (Extreme Value Type I) distributions.

Parameters ---------- x : array_like Array of sample data. dist : 'norm','expon','logistic','gumbel','gumbel_l', gumbel_r', 'extreme1', optional the type of distribution to test against. The default is 'norm' and 'extreme1', 'gumbel_l' and 'gumbel' are synonyms.

Returns ------- statistic : float The Anderson-Darling test statistic. critical_values : list The critical values for this distribution. significance_level : list The significance levels for the corresponding critical values in percents. The function returns critical values for a differing set of significance levels depending on the distribution that is being tested against.

See Also -------- kstest : The Kolmogorov-Smirnov test for goodness-of-fit.

Notes ----- Critical values provided are for the following significance levels:

normal/exponenential 15%, 10%, 5%, 2.5%, 1% logistic 25%, 10%, 5%, 2.5%, 1%, 0.5% Gumbel 25%, 10%, 5%, 2.5%, 1%

If the returned statistic is larger than these critical values then for the corresponding significance level, the null hypothesis that the data come from the chosen distribution can be rejected. The returned statistic is referred to as 'A2' in the references.

References ---------- .. 1 https://www.itl.nist.gov/div898/handbook/prc/section2/prc213.htm .. 2 Stephens, M. A. (1974). EDF Statistics for Goodness of Fit and Some Comparisons, Journal of the American Statistical Association, Vol. 69, pp. 730-737. .. 3 Stephens, M. A. (1976). Asymptotic Results for Goodness-of-Fit Statistics with Unknown Parameters, Annals of Statistics, Vol. 4, pp. 357-369. .. 4 Stephens, M. A. (1977). Goodness of Fit for the Extreme Value Distribution, Biometrika, Vol. 64, pp. 583-588. .. 5 Stephens, M. A. (1977). Goodness of Fit with Special Reference to Tests for Exponentiality , Technical Report No. 262, Department of Statistics, Stanford University, Stanford, CA. .. 6 Stephens, M. A. (1979). Tests of Fit for the Logistic Distribution Based on the Empirical Distribution Function, Biometrika, Vol. 66, pp. 591-595.

The Anderson-Darling test for k-samples.

The k-sample Anderson-Darling test is a modification of the one-sample Anderson-Darling test. It tests the null hypothesis that k-samples are drawn from the same population without having to specify the distribution function of that population. The critical values depend on the number of samples.

Parameters ---------- samples : sequence of 1-D array_like Array of sample data in arrays. midrank : bool, optional Type of Anderson-Darling test which is computed. Default (True) is the midrank test applicable to continuous and discrete populations. If False, the right side empirical distribution is used.

Returns ------- statistic : float Normalized k-sample Anderson-Darling test statistic. critical_values : array The critical values for significance levels 25%, 10%, 5%, 2.5%, 1%, 0.5%, 0.1%. significance_level : float An approximate significance level at which the null hypothesis for the provided samples can be rejected. The value is floored / capped at 0.1% / 25%.

Raises ------ ValueError If less than 2 samples are provided, a sample is empty, or no distinct observations are in the samples.

See Also -------- ks_2samp : 2 sample Kolmogorov-Smirnov test anderson : 1 sample Anderson-Darling test

Notes ----- 1_ defines three versions of the k-sample Anderson-Darling test: one for continuous distributions and two for discrete distributions, in which ties between samples may occur. The default of this routine is to compute the version based on the midrank empirical distribution function. This test is applicable to continuous and discrete data. If midrank is set to False, the right side empirical distribution is used for a test for discrete data. According to 1_, the two discrete test statistics differ only slightly if a few collisions due to round-off errors occur in the test not adjusted for ties between samples.

The critical values corresponding to the significance levels from 0.01 to 0.25 are taken from 1_. p-values are floored / capped at 0.1% / 25%. Since the range of critical values might be extended in future releases, it is recommended not to test ``p == 0.25``, but rather ``p >= 0.25`` (analogously for the lower bound).

.. versionadded:: 0.14.0

References ---------- .. 1 Scholz, F. W and Stephens, M. A. (1987), K-Sample Anderson-Darling Tests, Journal of the American Statistical Association, Vol. 82, pp. 918-924.

Examples -------- >>> from scipy import stats >>> np.random.seed(314159)

The null hypothesis that the two random samples come from the same distribution can be rejected at the 5% level because the returned test value is greater than the critical value for 5% (1.961) but not at the 2.5% level. The interpolation gives an approximate significance level of 3.2%:

>>> stats.anderson_ksamp(np.random.normal(size=50), ... np.random.normal(loc=0.5, size=30)) (2.4615796189876105, array( 0.325, 1.226, 1.961, 2.718, 3.752, 4.592, 6.546), 0.03176687568842282)

The null hypothesis cannot be rejected for three samples from an identical distribution. The reported p-value (25%) has been capped and may not be very accurate (since it corresponds to the value 0.449 whereas the statistic is -0.731):

>>> stats.anderson_ksamp(np.random.normal(size=50), ... np.random.normal(size=30), np.random.normal(size=20)) (-0.73091722665244196, array( 0.44925884, 1.3052767 , 1.9434184 , 2.57696569, 3.41634856, 4.07210043, 5.56419101), 0.25)

Perform the Ansari-Bradley test for equal scale parameters.

The Ansari-Bradley test is a non-parametric test for the equality of the scale parameter of the distributions from which two samples were drawn.

Parameters ---------- x, y : array_like Arrays of sample data.

Returns ------- statistic : float The Ansari-Bradley test statistic. pvalue : float The p-value of the hypothesis test.

See Also -------- fligner : A non-parametric test for the equality of k variances mood : A non-parametric test for the equality of two scale parameters

Notes ----- The p-value given is exact when the sample sizes are both less than 55 and there are no ties, otherwise a normal approximation for the p-value is used.

References ---------- .. 1 Sprent, Peter and N.C. Smeeton. Applied nonparametric statistical methods. 3rd ed. Chapman and Hall/CRC. 2001. Section 5.8.2.

Test whether any array element along a given axis evaluates to True.

Returns single boolean unless `axis` is not ``None``

Parameters ---------- a : array_like Input array or object that can be converted to an array. axis : None or int or tuple of ints, optional Axis or axes along which a logical OR reduction is performed. The default (``axis=None``) is to perform a logical OR over all the dimensions of the input array. `axis` may be negative, in which case it counts from the last to the first axis.

.. versionadded:: 1.7.0

If this is a tuple of ints, a reduction is performed on multiple axes, instead of a single axis or all the axes as before. out : ndarray, optional Alternate output array in which to place the result. It must have the same shape as the expected output and its type is preserved (e.g., if it is of type float, then it will remain so, returning 1.0 for True and 0.0 for False, regardless of the type of `a`). See `ufuncs-output-type` for more details.

keepdims : bool, optional If this is set to True, the axes which are reduced are left in the result as dimensions with size one. With this option, the result will broadcast correctly against the input array.

If the default value is passed, then `keepdims` will not be passed through to the `any` method of sub-classes of `ndarray`, however any non-default value will be. If the sub-class' method does not implement `keepdims` any exceptions will be raised.

Returns ------- any : bool or ndarray A new boolean or `ndarray` is returned unless `out` is specified, in which case a reference to `out` is returned.

See Also -------- ndarray.any : equivalent method

all : Test whether all elements along a given axis evaluate to True.

Notes ----- Not a Number (NaN), positive infinity and negative infinity evaluate to `True` because these are not equal to zero.

Examples -------- >>> np.any([True, False], [True, True]) True

>>> np.any([True, False], [False, False], axis=0) array( True, False)

>>> np.any(-1, 0, 5) True

>>> np.any(np.nan) True

>>> o=np.array(False) >>> z=np.any(-1, 4, 5, out=o) >>> z, o (array(True), array(True)) >>> # Check now that z is a reference to o >>> z is o True >>> id(z), id(o) # identity of z and o # doctest: +SKIP (191614240, 191614240)

arange(start, stop, step,, dtype=None)

Return evenly spaced values within a given interval.

Values are generated within the half-open interval ``start, stop)`` (in other words, the interval including `start` but excluding `stop`). For integer arguments the function is equivalent to the Python built-in `range` function, but returns an ndarray rather than a list. When using a non-integer step, such as 0.1, the results will often not be consistent. It is better to use `numpy.linspace` for these cases. Parameters ---------- start : number, optional Start of interval. The interval includes this value. The default start value is 0. stop : number End of interval. The interval does not include this value, except in some cases where `step` is not an integer and floating point round-off affects the length of `out`. step : number, optional Spacing between values. For any output `out`, this is the distance between two adjacent values, ``out[i+1] - out[i]``. The default step size is 1. If `step` is specified as a position argument, `start` must also be given. dtype : dtype The type of the output array. If `dtype` is not given, infer the data type from the other input arguments. Returns ------- arange : ndarray Array of evenly spaced values. For floating point arguments, the length of the result is ``ceil((stop - start)/step)``. Because of floating point overflow, this rule may result in the last element of `out` being greater than `stop`. See Also -------- numpy.linspace : Evenly spaced numbers with careful handling of endpoints. numpy.ogrid: Arrays of evenly spaced numbers in N-dimensions. numpy.mgrid: Grid-shaped arrays of evenly spaced numbers in N-dimensions. Examples -------- >>> np.arange(3) array([0, 1, 2]) >>> np.arange(3.0) array([ 0., 1., 2.]) >>> np.arange(3,7) array([3, 4, 5, 6]) >>> np.arange(3,7,2) array([3, 5])

arctan2(x1, x2, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True, signature, extobj)

Element-wise arc tangent of ``x1/x2`` choosing the quadrant correctly.

The quadrant (i.e., branch) is chosen so that ``arctan2(x1, x2)`` is the signed angle in radians between the ray ending at the origin and passing through the point (1,0), and the ray ending at the origin and passing through the point (`x2`, `x1`). (Note the role reversal: the '`y`-coordinate' is the first function parameter, the '`x`-coordinate' is the second.) By IEEE convention, this function is defined for `x2` = +/-0 and for either or both of `x1` and `x2` = +/-inf (see Notes for specific values).

This function is not defined for complex-valued arguments; for the so-called argument of complex values, use `angle`.

Parameters ---------- x1 : array_like, real-valued `y`-coordinates. x2 : array_like, real-valued `x`-coordinates. If ``x1.shape != x2.shape``, they must be broadcastable to a common shape (which becomes the shape of the output). out : ndarray, None, or tuple of ndarray and None, optional A location into which the result is stored. If provided, it must have a shape that the inputs broadcast to. If not provided or None, a freshly-allocated array is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs. where : array_like, optional This condition is broadcast over the input. At locations where the condition is True, the `out` array will be set to the ufunc result. Elsewhere, the `out` array will retain its original value. Note that if an uninitialized `out` array is created via the default ``out=None``, locations within it where the condition is False will remain uninitialized. **kwargs For other keyword-only arguments, see the :ref:`ufunc docs <ufuncs.kwargs>`.

Returns ------- angle : ndarray Array of angles in radians, in the range ``-pi, pi``. This is a scalar if both `x1` and `x2` are scalars.

See Also -------- arctan, tan, angle

Notes ----- *arctan2* is identical to the `atan2` function of the underlying C library. The following special values are defined in the C standard: 1_

====== ====== ================ `x1` `x2` `arctan2(x1,x2)` ====== ====== ================ +/- 0 +0 +/- 0 +/- 0 -0 +/- pi > 0 +/-inf +0 / +pi < 0 +/-inf -0 / -pi +/-inf +inf +/- (pi/4) +/-inf -inf +/- (3*pi/4) ====== ====== ================

Note that +0 and -0 are distinct floating point numbers, as are +inf and -inf.

References ---------- .. 1 ISO/IEC standard 9899:1999, 'Programming language C.'

Examples -------- Consider four points in different quadrants:

>>> x = np.array(-1, +1, +1, -1) >>> y = np.array(-1, -1, +1, +1) >>> np.arctan2(y, x) * 180 / np.pi array(-135., -45., 45., 135.)

Note the order of the parameters. `arctan2` is defined also when `x2` = 0 and at several other special points, obtaining values in the range ``-pi, pi``:

>>> np.arctan2(1., -1., 0., 0.) array( 1.57079633, -1.57079633) >>> np.arctan2(0., 0., np.inf, +0., -0., np.inf) array( 0. , 3.14159265, 0.78539816)

Evenly round to the given number of decimals.

Parameters ---------- a : array_like Input data. decimals : int, optional Number of decimal places to round to (default: 0). If decimals is negative, it specifies the number of positions to the left of the decimal point. out : ndarray, optional Alternative output array in which to place the result. It must have the same shape as the expected output, but the type of the output values will be cast if necessary. See `ufuncs-output-type` for more details.

Returns ------- rounded_array : ndarray An array of the same type as `a`, containing the rounded values. Unless `out` was specified, a new array is created. A reference to the result is returned.

The real and imaginary parts of complex numbers are rounded separately. The result of rounding a float is a float.

See Also -------- ndarray.round : equivalent method

ceil, fix, floor, rint, trunc

Notes ----- For values exactly halfway between rounded decimal values, NumPy rounds to the nearest even value. Thus 1.5 and 2.5 round to 2.0, -0.5 and 0.5 round to 0.0, etc.

``np.around`` uses a fast but sometimes inexact algorithm to round floating-point datatypes. For positive `decimals` it is equivalent to ``np.true_divide(np.rint(a * 10**decimals), 10**decimals)``, which has error due to the inexact representation of decimal fractions in the IEEE floating point standard 1_ and errors introduced when scaling by powers of ten. For instance, note the extra '1' in the following:

>>> np.round(56294995342131.5, 3) 56294995342131.51

If your goal is to print such values with a fixed number of decimals, it is preferable to use numpy's float printing routines to limit the number of printed decimals:

>>> np.format_float_positional(56294995342131.5, precision=3) '56294995342131.5'

The float printing routines use an accurate but much more computationally demanding algorithm to compute the number of digits after the decimal point.

Alternatively, Python's builtin `round` function uses a more accurate but slower algorithm for 64-bit floating point values:

>>> round(56294995342131.5, 3) 56294995342131.5 >>> np.round(16.055, 2), round(16.055, 2) # equals 16.0549999999999997 (16.06, 16.05)

References ---------- .. 1 'Lecture Notes on the Status of IEEE 754', William Kahan, https://people.eecs.berkeley.edu/~wkahan/ieee754status/IEEE754.PDF .. 2 'How Futile are Mindless Assessments of Roundoff in Floating-Point Computation?', William Kahan, https://people.eecs.berkeley.edu/~wkahan/Mindless.pdf

Examples -------- >>> np.around(0.37, 1.64) array(0., 2.) >>> np.around(0.37, 1.64, decimals=1) array(0.4, 1.6) >>> np.around(.5, 1.5, 2.5, 3.5, 4.5) # rounds to nearest even value array(0., 2., 2., 4., 4.) >>> np.around(1,2,3,11, decimals=1) # ndarray of ints is returned array( 1, 2, 3, 11) >>> np.around(1,2,3,11, decimals=-1) array( 0, 0, 0, 10)

array(object, dtype=None, copy=True, order='K', subok=False, ndmin=0)

Create an array.

Parameters ---------- object : array_like An array, any object exposing the array interface, an object whose __array__ method returns an array, or any (nested) sequence. dtype : data-type, optional The desired data-type for the array. If not given, then the type will be determined as the minimum type required to hold the objects in the sequence. copy : bool, optional If true (default), then the object is copied. Otherwise, a copy will only be made if __array__ returns a copy, if obj is a nested sequence, or if a copy is needed to satisfy any of the other requirements (`dtype`, `order`, etc.). order : 'K', 'A', 'C', 'F', optional Specify the memory layout of the array. If object is not an array, the newly created array will be in C order (row major) unless 'F' is specified, in which case it will be in Fortran order (column major). If object is an array the following holds.

===== ========= =================================================== order no copy copy=True ===== ========= =================================================== 'K' unchanged F & C order preserved, otherwise most similar order 'A' unchanged F order if input is F and not C, otherwise C order 'C' C order C order 'F' F order F order ===== ========= ===================================================

When ``copy=False`` and a copy is made for other reasons, the result is the same as if ``copy=True``, with some exceptions for `A`, see the Notes section. The default order is 'K'. subok : bool, optional If True, then sub-classes will be passed-through, otherwise the returned array will be forced to be a base-class array (default). ndmin : int, optional Specifies the minimum number of dimensions that the resulting array should have. Ones will be pre-pended to the shape as needed to meet this requirement.

Returns ------- out : ndarray An array object satisfying the specified requirements.

See Also -------- empty_like : Return an empty array with shape and type of input. ones_like : Return an array of ones with shape and type of input. zeros_like : Return an array of zeros with shape and type of input. full_like : Return a new array with shape of input filled with value. empty : Return a new uninitialized array. ones : Return a new array setting values to one. zeros : Return a new array setting values to zero. full : Return a new array of given shape filled with value.

Notes ----- When order is 'A' and `object` is an array in neither 'C' nor 'F' order, and a copy is forced by a change in dtype, then the order of the result is not necessarily 'C' as expected. This is likely a bug.

Examples -------- >>> np.array(1, 2, 3) array(1, 2, 3)

Upcasting:

>>> np.array(1, 2, 3.0) array( 1., 2., 3.)

More than one dimension:

>>> np.array([1, 2], [3, 4]) array([1, 2], [3, 4])

Minimum dimensions 2:

>>> np.array(1, 2, 3, ndmin=2) array([1, 2, 3])

Type provided:

>>> np.array(1, 2, 3, dtype=complex) array( 1.+0.j, 2.+0.j, 3.+0.j)

Data-type consisting of more than one element:

>>> x = np.array((1,2),(3,4),dtype=('a','<i4'),('b','<i4')) >>> x'a' array(1, 3)

Creating an array from sub-classes:

>>> np.array(np.mat('1 2; 3 4')) array([1, 2], [3, 4])

>>> np.array(np.mat('1 2; 3 4'), subok=True) matrix([1, 2], [3, 4])

Convert the input to an array.

Parameters ---------- a : array_like Input data, in any form that can be converted to an array. This includes lists, lists of tuples, tuples, tuples of tuples, tuples of lists and ndarrays. dtype : data-type, optional By default, the data-type is inferred from the input data. order : 'C', 'F', optional Whether to use row-major (C-style) or column-major (Fortran-style) memory representation. Defaults to 'C'.

Returns ------- out : ndarray Array interpretation of `a`. No copy is performed if the input is already an ndarray with matching dtype and order. If `a` is a subclass of ndarray, a base class ndarray is returned.

See Also -------- asanyarray : Similar function which passes through subclasses. ascontiguousarray : Convert input to a contiguous array. asfarray : Convert input to a floating point ndarray. asfortranarray : Convert input to an ndarray with column-major memory order. asarray_chkfinite : Similar function which checks input for NaNs and Infs. fromiter : Create an array from an iterator. fromfunction : Construct an array by executing a function on grid positions.

Examples -------- Convert a list into an array:

>>> a = 1, 2 >>> np.asarray(a) array(1, 2)

Existing arrays are not copied:

>>> a = np.array(1, 2) >>> np.asarray(a) is a True

If `dtype` is set, array is copied only if dtype does not match:

>>> a = np.array(1, 2, dtype=np.float32) >>> np.asarray(a, dtype=np.float32) is a True >>> np.asarray(a, dtype=np.float64) is a False

Contrary to `asanyarray`, ndarray subclasses are not passed through:

>>> issubclass(np.recarray, np.ndarray) True >>> a = np.array((1.0, 2), (3.0, 4), dtype='f4,i4').view(np.recarray) >>> np.asarray(a) is a False >>> np.asanyarray(a) is a True

Convert inputs to arrays with at least one dimension.

Scalar inputs are converted to 1-dimensional arrays, whilst higher-dimensional inputs are preserved.

Parameters ---------- arys1, arys2, ... : array_like One or more input arrays.

Returns ------- ret : ndarray An array, or list of arrays, each with ``a.ndim >= 1``. Copies are made only if necessary.

See Also -------- atleast_2d, atleast_3d

Examples -------- >>> np.atleast_1d(1.0) array(1.)

>>> x = np.arange(9.0).reshape(3,3) >>> np.atleast_1d(x) array([0., 1., 2.], [3., 4., 5.], [6., 7., 8.]) >>> np.atleast_1d(x) is x True

>>> np.atleast_1d(1, 3, 4) array([1]), array([3, 4])

Perform Bartlett's test for equal variances.

Bartlett's test tests the null hypothesis that all input samples are from populations with equal variances. For samples from significantly non-normal populations, Levene's test `levene` is more robust.

Parameters ---------- sample1, sample2,... : array_like arrays of sample data. Only 1d arrays are accepted, they may have different lengths.

Returns ------- statistic : float The test statistic. pvalue : float The p-value of the test.

See Also -------- fligner : A non-parametric test for the equality of k variances levene : A robust parametric test for equality of k variances

Notes ----- Conover et al. (1981) examine many of the existing parametric and nonparametric tests by extensive simulations and they conclude that the tests proposed by Fligner and Killeen (1976) and Levene (1960) appear to be superior in terms of robustness of departures from normality and power (3_).

References ---------- .. 1 https://www.itl.nist.gov/div898/handbook/eda/section3/eda357.htm

.. 2 Snedecor, George W. and Cochran, William G. (1989), Statistical Methods, Eighth Edition, Iowa State University Press.

.. 3 Park, C. and Lindsay, B. G. (1999). Robust Scale Estimation and Hypothesis Testing based on Quadratic Inference Function. Technical Report #99-03, Center for Likelihood Studies, Pennsylvania State University.

.. 4 Bartlett, M. S. (1937). Properties of Sufficiency and Statistical Tests. Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, Vol. 160, No.901, pp. 268-282.

Bayesian confidence intervals for the mean, var, and std.

Parameters ---------- data : array_like Input data, if multi-dimensional it is flattened to 1-D by `bayes_mvs`. Requires 2 or more data points. alpha : float, optional Probability that the returned confidence interval contains the true parameter.

Returns ------- mean_cntr, var_cntr, std_cntr : tuple The three results are for the mean, variance and standard deviation, respectively. Each result is a tuple of the form::

(center, (lower, upper))

with `center` the mean of the conditional pdf of the value given the data, and `(lower, upper)` a confidence interval, centered on the median, containing the estimate to a probability ``alpha``.

See Also -------- mvsdist

Notes ----- Each tuple of mean, variance, and standard deviation estimates represent the (center, (lower, upper)) with center the mean of the conditional pdf of the value given the data and (lower, upper) is a confidence interval centered on the median, containing the estimate to a probability ``alpha``.

Converts data to 1-D and assumes all data has the same mean and variance. Uses Jeffrey's prior for variance and std.

Equivalent to ``tuple((x.mean(), x.interval(alpha)) for x in mvsdist(dat))``

References ---------- T.E. Oliphant, 'A Bayesian perspective on estimating mean, variance, and standard-deviation from data', https://scholarsarchive.byu.edu/facpub/278, 2006.

Examples -------- First a basic example to demonstrate the outputs:

>>> from scipy import stats >>> data = 6, 9, 12, 7, 8, 8, 13 >>> mean, var, std = stats.bayes_mvs(data) >>> mean Mean(statistic=9.0, minmax=(7.103650222612533, 10.896349777387467)) >>> var Variance(statistic=10.0, minmax=(3.176724206..., 24.45910382...)) >>> std Std_dev(statistic=2.9724954732045084, minmax=(1.7823367265645143, 4.945614605014631))

Now we generate some normally distributed random data, and get estimates of mean and standard deviation with 95% confidence intervals for those estimates:

>>> n_samples = 100000 >>> data = stats.norm.rvs(size=n_samples) >>> res_mean, res_var, res_std = stats.bayes_mvs(data, alpha=0.95)

>>> import matplotlib.pyplot as plt >>> fig = plt.figure() >>> ax = fig.add_subplot(111) >>> ax.hist(data, bins=100, density=True, label='Histogram of data') >>> ax.vlines(res_mean.statistic, 0, 0.5, colors='r', label='Estimated mean') >>> ax.axvspan(res_mean.minmax0,res_mean.minmax1, facecolor='r', ... alpha=0.2, label=r'Estimated mean (95% limits)') >>> ax.vlines(res_std.statistic, 0, 0.5, colors='g', label='Estimated scale') >>> ax.axvspan(res_std.minmax0,res_std.minmax1, facecolor='g', alpha=0.2, ... label=r'Estimated scale (95% limits)')

>>> ax.legend(fontsize=10) >>> ax.set_xlim(-4, 4) >>> ax.set_ylim(0, 0.5) >>> plt.show()

Perform a test that the probability of success is p.

This is an exact, two-sided test of the null hypothesis that the probability of success in a Bernoulli experiment is `p`.

Parameters ---------- x : int or array_like The number of successes, or if x has length 2, it is the number of successes and the number of failures. n : int The number of trials. This is ignored if x gives both the number of successes and failures. p : float, optional The hypothesized probability of success. ``0 <= p <= 1``. The default value is ``p = 0.5``. alternative : 'two-sided', 'greater', 'less', optional Indicates the alternative hypothesis. The default value is 'two-sided'.

Returns ------- p-value : float The p-value of the hypothesis test.

References ---------- .. 1 https://en.wikipedia.org/wiki/Binomial_test

Examples -------- >>> from scipy import stats

A car manufacturer claims that no more than 10% of their cars are unsafe. 15 cars are inspected for safety, 3 were found to be unsafe. Test the manufacturer's claim:

>>> stats.binom_test(3, n=15, p=0.1, alternative='greater') 0.18406106910639114

The null hypothesis cannot be rejected at the 5% level of significance because the returned p-value is greater than the critical value of 5%.

Return a dataset transformed by a Box-Cox power transformation.

Parameters ---------- x : ndarray Input array. Must be positive 1-dimensional. Must not be constant. lmbda : None, scalar, optional If `lmbda` is not None, do the transformation for that value.

If `lmbda` is None, find the lambda that maximizes the log-likelihood function and return it as the second output argument. alpha : None, float, optional If ``alpha`` is not None, return the ``100 * (1-alpha)%`` confidence interval for `lmbda` as the third output argument. Must be between 0.0 and 1.0.

Returns ------- boxcox : ndarray Box-Cox power transformed array. maxlog : float, optional If the `lmbda` parameter is None, the second returned argument is the lambda that maximizes the log-likelihood function. (min_ci, max_ci) : tuple of float, optional If `lmbda` parameter is None and ``alpha`` is not None, this returned tuple of floats represents the minimum and maximum confidence limits given ``alpha``.

See Also -------- probplot, boxcox_normplot, boxcox_normmax, boxcox_llf

Notes ----- The Box-Cox transform is given by::

y = (x**lmbda - 1) / lmbda, for lmbda > 0 log(x), for lmbda = 0

`boxcox` requires the input data to be positive. Sometimes a Box-Cox transformation provides a shift parameter to achieve this; `boxcox` does not. Such a shift parameter is equivalent to adding a positive constant to `x` before calling `boxcox`.

The confidence limits returned when ``alpha`` is provided give the interval where:

.. math::

llf(\hat\lambda) - llf(\lambda) < \frac

\chi^2(1 - \alpha, 1),

with ``llf`` the log-likelihood function and :math:`\chi^2` the chi-squared function.

References ---------- G.E.P. Box and D.R. Cox, 'An Analysis of Transformations', Journal of the Royal Statistical Society B, 26, 211-252 (1964).

Examples -------- >>> from scipy import stats >>> import matplotlib.pyplot as plt

We generate some random variates from a non-normal distribution and make a probability plot for it, to show it is non-normal in the tails:

>>> fig = plt.figure() >>> ax1 = fig.add_subplot(211) >>> x = stats.loggamma.rvs(5, size=500) + 5 >>> prob = stats.probplot(x, dist=stats.norm, plot=ax1) >>> ax1.set_xlabel('') >>> ax1.set_title('Probplot against normal distribution')

We now use `boxcox` to transform the data so it's closest to normal:

>>> ax2 = fig.add_subplot(212) >>> xt, _ = stats.boxcox(x) >>> prob = stats.probplot(xt, dist=stats.norm, plot=ax2) >>> ax2.set_title('Probplot after Box-Cox transformation')

>>> plt.show()

The boxcox log-likelihood function.

Parameters ---------- lmb : scalar Parameter for Box-Cox transformation. See `boxcox` for details. data : array_like Data to calculate Box-Cox log-likelihood for. If `data` is multi-dimensional, the log-likelihood is calculated along the first axis.

Returns ------- llf : float or ndarray Box-Cox log-likelihood of `data` given `lmb`. A float for 1-D `data`, an array otherwise.

See Also -------- boxcox, probplot, boxcox_normplot, boxcox_normmax

Notes ----- The Box-Cox log-likelihood function is defined here as

.. math::

llf = (\lambda - 1) \sum_i(\log(x_i)) - N/2 \log(\sum_i (y_i - \bary)^2 / N),

where ``y`` is the Box-Cox transformed input data ``x``.

Examples -------- >>> from scipy import stats >>> import matplotlib.pyplot as plt >>> from mpl_toolkits.axes_grid1.inset_locator import inset_axes >>> np.random.seed(1245)

Generate some random variates and calculate Box-Cox log-likelihood values for them for a range of ``lmbda`` values:

>>> x = stats.loggamma.rvs(5, loc=10, size=1000) >>> lmbdas = np.linspace(-2, 10) >>> llf = np.zeros(lmbdas.shape, dtype=float) >>> for ii, lmbda in enumerate(lmbdas): ... llfii = stats.boxcox_llf(lmbda, x)

Also find the optimal lmbda value with `boxcox`:

>>> x_most_normal, lmbda_optimal = stats.boxcox(x)

Plot the log-likelihood as function of lmbda. Add the optimal lmbda as a horizontal line to check that that's really the optimum:

>>> fig = plt.figure() >>> ax = fig.add_subplot(111) >>> ax.plot(lmbdas, llf, 'b.-') >>> ax.axhline(stats.boxcox_llf(lmbda_optimal, x), color='r') >>> ax.set_xlabel('lmbda parameter') >>> ax.set_ylabel('Box-Cox log-likelihood')

Now add some probability plots to show that where the log-likelihood is maximized the data transformed with `boxcox` looks closest to normal:

>>> locs = 3, 10, 4 # 'lower left', 'center', 'lower right' >>> for lmbda, loc in zip(-1, lmbda_optimal, 9, locs): ... xt = stats.boxcox(x, lmbda=lmbda) ... (osm, osr), (slope, intercept, r_sq) = stats.probplot(xt) ... ax_inset = inset_axes(ax, width='20%', height='20%', loc=loc) ... ax_inset.plot(osm, osr, 'c.', osm, slope*osm + intercept, 'k-') ... ax_inset.set_xticklabels() ... ax_inset.set_yticklabels() ... ax_inset.set_title(r'$\lambda=%1.2f$' % lmbda)

>>> plt.show()

Compute optimal Box-Cox transform parameter for input data.

Parameters ---------- x : array_like Input array. brack : 2-tuple, optional The starting interval for a downhill bracket search with `optimize.brent`. Note that this is in most cases not critical; the final result is allowed to be outside this bracket. method : str, optional The method to determine the optimal transform parameter (`boxcox` ``lmbda`` parameter). Options are:

'pearsonr' (default) Maximizes the Pearson correlation coefficient between ``y = boxcox(x)`` and the expected values for ``y`` if `x` would be normally-distributed.

'mle' Minimizes the log-likelihood `boxcox_llf`. This is the method used in `boxcox`.

'all' Use all optimization methods available, and return all results. Useful to compare different methods.

Returns ------- maxlog : float or ndarray The optimal transform parameter found. An array instead of a scalar for ``method='all'``.

See Also -------- boxcox, boxcox_llf, boxcox_normplot

Examples -------- >>> from scipy import stats >>> import matplotlib.pyplot as plt >>> np.random.seed(1234) # make this example reproducible

Generate some data and determine optimal ``lmbda`` in various ways:

>>> x = stats.loggamma.rvs(5, size=30) + 5 >>> y, lmax_mle = stats.boxcox(x) >>> lmax_pearsonr = stats.boxcox_normmax(x)

>>> lmax_mle 7.177... >>> lmax_pearsonr 7.916... >>> stats.boxcox_normmax(x, method='all') array( 7.91667384, 7.17718692)

>>> fig = plt.figure() >>> ax = fig.add_subplot(111) >>> prob = stats.boxcox_normplot(x, -10, 10, plot=ax) >>> ax.axvline(lmax_mle, color='r') >>> ax.axvline(lmax_pearsonr, color='g', ls='--')

>>> plt.show()

Compute parameters for a Box-Cox normality plot, optionally show it.

A Box-Cox normality plot shows graphically what the best transformation parameter is to use in `boxcox` to obtain a distribution that is close to normal.

Parameters ---------- x : array_like Input array. la, lb : scalar The lower and upper bounds for the ``lmbda`` values to pass to `boxcox` for Box-Cox transformations. These are also the limits of the horizontal axis of the plot if that is generated. plot : object, optional If given, plots the quantiles and least squares fit. `plot` is an object that has to have methods 'plot' and 'text'. The `matplotlib.pyplot` module or a Matplotlib Axes object can be used, or a custom object with the same methods. Default is None, which means that no plot is created. N : int, optional Number of points on the horizontal axis (equally distributed from `la` to `lb`).

Returns ------- lmbdas : ndarray The ``lmbda`` values for which a Box-Cox transform was done. ppcc : ndarray Probability Plot Correlelation Coefficient, as obtained from `probplot` when fitting the Box-Cox transformed input `x` against a normal distribution.

See Also -------- probplot, boxcox, boxcox_normmax, boxcox_llf, ppcc_max

Notes ----- Even if `plot` is given, the figure is not shown or saved by `boxcox_normplot`; ``plt.show()`` or ``plt.savefig('figname.png')`` should be used after calling `probplot`.

Examples -------- >>> from scipy import stats >>> import matplotlib.pyplot as plt

Generate some non-normally distributed data, and create a Box-Cox plot:

>>> x = stats.loggamma.rvs(5, size=500) + 5 >>> fig = plt.figure() >>> ax = fig.add_subplot(111) >>> prob = stats.boxcox_normplot(x, -20, 20, plot=ax)

Determine and plot the optimal ``lmbda`` to transform ``x`` and plot it in the same plot:

>>> _, maxlog = stats.boxcox(x) >>> ax.axvline(maxlog, color='r')

>>> plt.show()

ceil(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True, signature, extobj)

Return the ceiling of the input, element-wise.

The ceil of the scalar `x` is the smallest integer `i`, such that `i >= x`. It is often denoted as :math:`\lceil x \rceil`.

Parameters ---------- x : array_like Input data. out : ndarray, None, or tuple of ndarray and None, optional A location into which the result is stored. If provided, it must have a shape that the inputs broadcast to. If not provided or None, a freshly-allocated array is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs. where : array_like, optional This condition is broadcast over the input. At locations where the condition is True, the `out` array will be set to the ufunc result. Elsewhere, the `out` array will retain its original value. Note that if an uninitialized `out` array is created via the default ``out=None``, locations within it where the condition is False will remain uninitialized. **kwargs For other keyword-only arguments, see the :ref:`ufunc docs <ufuncs.kwargs>`.

Returns ------- y : ndarray or scalar The ceiling of each element in `x`, with `float` dtype. This is a scalar if `x` is a scalar.

See Also -------- floor, trunc, rint

Examples -------- >>> a = np.array(-1.7, -1.5, -0.2, 0.2, 1.5, 1.7, 2.0) >>> np.ceil(a) array(-1., -1., -0., 1., 2., 2., 2.)

Chi-square test of independence of variables in a contingency table.

This function computes the chi-square statistic and p-value for the hypothesis test of independence of the observed frequencies in the contingency table 1_ `observed`. The expected frequencies are computed based on the marginal sums under the assumption of independence; see `scipy.stats.contingency.expected_freq`. The number of degrees of freedom is (expressed using numpy functions and attributes)::

dof = observed.size - sum(observed.shape) + observed.ndim - 1

Parameters ---------- observed : array_like The contingency table. The table contains the observed frequencies (i.e. number of occurrences) in each category. In the two-dimensional case, the table is often described as an 'R x C table'. correction : bool, optional If True, *and* the degrees of freedom is 1, apply Yates' correction for continuity. The effect of the correction is to adjust each observed value by 0.5 towards the corresponding expected value. lambda_ : float or str, optional. By default, the statistic computed in this test is Pearson's chi-squared statistic 2_. `lambda_` allows a statistic from the Cressie-Read power divergence family 3_ to be used instead. See `power_divergence` for details.

Returns ------- chi2 : float The test statistic. p : float The p-value of the test dof : int Degrees of freedom expected : ndarray, same shape as `observed` The expected frequencies, based on the marginal sums of the table.

See Also -------- contingency.expected_freq fisher_exact chisquare power_divergence

Notes ----- An often quoted guideline for the validity of this calculation is that the test should be used only if the observed and expected frequencies in each cell are at least 5.

This is a test for the independence of different categories of a population. The test is only meaningful when the dimension of `observed` is two or more. Applying the test to a one-dimensional table will always result in `expected` equal to `observed` and a chi-square statistic equal to 0.

This function does not handle masked arrays, because the calculation does not make sense with missing values.

Like stats.chisquare, this function computes a chi-square statistic; the convenience this function provides is to figure out the expected frequencies and degrees of freedom from the given contingency table. If these were already known, and if the Yates' correction was not required, one could use stats.chisquare. That is, if one calls::

chi2, p, dof, ex = chi2_contingency(obs, correction=False)

then the following is true::

(chi2, p) == stats.chisquare(obs.ravel(), f_exp=ex.ravel(), ddof=obs.size - 1 - dof)

The `lambda_` argument was added in version 0.13.0 of scipy.

References ---------- .. 1 'Contingency table', https://en.wikipedia.org/wiki/Contingency_table .. 2 'Pearson's chi-squared test', https://en.wikipedia.org/wiki/Pearson%27s_chi-squared_test .. 3 Cressie, N. and Read, T. R. C., 'Multinomial Goodness-of-Fit Tests', J. Royal Stat. Soc. Series B, Vol. 46, No. 3 (1984), pp. 440-464.

Examples -------- A two-way example (2 x 3):

>>> from scipy.stats import chi2_contingency >>> obs = np.array([10, 10, 20], [20, 20, 20]) >>> chi2_contingency(obs) (2.7777777777777777, 0.24935220877729619, 2, array([ 12., 12., 16.], [ 18., 18., 24.]))

Perform the test using the log-likelihood ratio (i.e. the 'G-test') instead of Pearson's chi-squared statistic.

>>> g, p, dof, expctd = chi2_contingency(obs, lambda_='log-likelihood') >>> g, p (2.7688587616781319, 0.25046668010954165)

A four-way example (2 x 2 x 2 x 2):

>>> obs = np.array( ... [[[12, 17], ... [11, 16]], ... [[11, 12], ... [15, 16]]], ... [[[23, 15], ... [30, 22]], ... [[14, 17], ... [15, 16]]]) >>> chi2_contingency(obs) (8.7584514426741897, 0.64417725029295503, 11, array([[[ 14.15462386, 14.15462386], [ 16.49423111, 16.49423111]], [[ 11.2461395 , 11.2461395 ], [ 13.10500554, 13.10500554]]], [[[ 19.5591166 , 19.5591166 ], [ 22.79202844, 22.79202844]], [[ 15.54012004, 15.54012004], [ 18.10873492, 18.10873492]]]))

Compute the circular mean for samples in a range.

Parameters ---------- samples : array_like Input array. high : float or int, optional High boundary for circular mean range. Default is ``2*pi``. low : float or int, optional Low boundary for circular mean range. Default is 0. axis : int, optional Axis along which means are computed. The default is to compute the mean of the flattened array. nan_policy : 'propagate', 'raise', 'omit', optional Defines how to handle when input contains nan. 'propagate' returns nan, 'raise' throws an error, 'omit' performs the calculations ignoring nan values. Default is 'propagate'.

Returns ------- circmean : float Circular mean.

Examples -------- >>> from scipy.stats import circmean >>> circmean(0.1, 2*np.pi+0.2, 6*np.pi+0.3) 0.2

>>> from scipy.stats import circmean >>> circmean(0.2, 1.4, 2.6, high = 1, low = 0) 0.4

Compute the circular standard deviation for samples assumed to be in the range low to high.

Parameters ---------- samples : array_like Input array. high : float or int, optional High boundary for circular standard deviation range. Default is ``2*pi``. low : float or int, optional Low boundary for circular standard deviation range. Default is 0. axis : int, optional Axis along which standard deviations are computed. The default is to compute the standard deviation of the flattened array. nan_policy : 'propagate', 'raise', 'omit', optional Defines how to handle when input contains nan. 'propagate' returns nan, 'raise' throws an error, 'omit' performs the calculations ignoring nan values. Default is 'propagate'.

Returns ------- circstd : float Circular standard deviation.

Notes ----- This uses a definition of circular standard deviation that in the limit of small angles returns a number close to the 'linear' standard deviation.

Examples -------- >>> from scipy.stats import circstd >>> circstd(0, 0.1*np.pi/2, 0.001*np.pi, 0.03*np.pi/2) 0.063564063306

Compute the circular variance for samples assumed to be in a range.

Parameters ---------- samples : array_like Input array. high : float or int, optional High boundary for circular variance range. Default is ``2*pi``. low : float or int, optional Low boundary for circular variance range. Default is 0. axis : int, optional Axis along which variances are computed. The default is to compute the variance of the flattened array. nan_policy : 'propagate', 'raise', 'omit', optional Defines how to handle when input contains nan. 'propagate' returns nan, 'raise' throws an error, 'omit' performs the calculations ignoring nan values. Default is 'propagate'.

Returns ------- circvar : float Circular variance.

Notes ----- This uses a definition of circular variance that in the limit of small angles returns a number close to the 'linear' variance.

Examples -------- >>> from scipy.stats import circvar >>> circvar(0, 2*np.pi/3, 5*np.pi/3) 2.19722457734

Return selected slices of an array along given axis.

When working along a given axis, a slice along that axis is returned in `output` for each index where `condition` evaluates to True. When working on a 1-D array, `compress` is equivalent to `extract`.

Parameters ---------- condition : 1-D array of bools Array that selects which entries to return. If len(condition) is less than the size of `a` along the given axis, then output is truncated to the length of the condition array. a : array_like Array from which to extract a part. axis : int, optional Axis along which to take slices. If None (default), work on the flattened array. out : ndarray, optional Output array. Its type is preserved and it must be of the right shape to hold the output.

Returns ------- compressed_array : ndarray A copy of `a` without the slices along axis for which `condition` is false.

See Also -------- take, choose, diag, diagonal, select ndarray.compress : Equivalent method in ndarray np.extract: Equivalent method when working on 1-D arrays ufuncs-output-type

Examples -------- >>> a = np.array([1, 2], [3, 4], [5, 6]) >>> a array([1, 2], [3, 4], [5, 6]) >>> np.compress(0, 1, a, axis=0) array([3, 4]) >>> np.compress(False, True, True, a, axis=0) array([3, 4], [5, 6]) >>> np.compress(False, True, a, axis=1) array([2], [4], [6])

Working on the flattened array does not return slices along an axis but selects elements.

>>> np.compress(False, True, a) array(2)

cos(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True, signature, extobj)

Cosine element-wise.

Parameters ---------- x : array_like Input array in radians. out : ndarray, None, or tuple of ndarray and None, optional A location into which the result is stored. If provided, it must have a shape that the inputs broadcast to. If not provided or None, a freshly-allocated array is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs. where : array_like, optional This condition is broadcast over the input. At locations where the condition is True, the `out` array will be set to the ufunc result. Elsewhere, the `out` array will retain its original value. Note that if an uninitialized `out` array is created via the default ``out=None``, locations within it where the condition is False will remain uninitialized. **kwargs For other keyword-only arguments, see the :ref:`ufunc docs <ufuncs.kwargs>`.

Returns ------- y : ndarray The corresponding cosine values. This is a scalar if `x` is a scalar.

Notes ----- If `out` is provided, the function writes the result into it, and returns a reference to `out`. (See Examples)

References ---------- M. Abramowitz and I. A. Stegun, Handbook of Mathematical Functions. New York, NY: Dover, 1972.

Examples -------- >>> np.cos(np.array(0, np.pi/2, np.pi)) array( 1.00000000e+00, 6.12303177e-17, -1.00000000e+00) >>> >>> # Example of providing the optional output parameter >>> out1 = np.array(0, dtype='d') >>> out2 = np.cos(0.1, out1) >>> out2 is out1 True >>> >>> # Example of ValueError due to provision of shape mis-matched `out` >>> np.cos(np.zeros((3,3)),np.zeros((2,2))) Traceback (most recent call last): File '<stdin>', line 1, in <module> ValueError: operands could not be broadcast together with shapes (3,3) (2,2)

Counts the number of non-zero values in the array ``a``.

The word 'non-zero' is in reference to the Python 2.x built-in method ``__nonzero__()`` (renamed ``__bool__()`` in Python 3.x) of Python objects that tests an object's 'truthfulness'. For example, any number is considered truthful if it is nonzero, whereas any string is considered truthful if it is not the empty string. Thus, this function (recursively) counts how many elements in ``a`` (and in sub-arrays thereof) have their ``__nonzero__()`` or ``__bool__()`` method evaluated to ``True``.

Parameters ---------- a : array_like The array for which to count non-zeros. axis : int or tuple, optional Axis or tuple of axes along which to count non-zeros. Default is None, meaning that non-zeros will be counted along a flattened version of ``a``.

.. versionadded:: 1.12.0

Returns ------- count : int or array of int Number of non-zero values in the array along a given axis. Otherwise, the total number of non-zero values in the array is returned.

See Also -------- nonzero : Return the coordinates of all the non-zero values.

Examples -------- >>> np.count_nonzero(np.eye(4)) 4 >>> np.count_nonzero([0,1,7,0,0],[3,0,0,2,19]) 5 >>> np.count_nonzero([0,1,7,0,0],[3,0,0,2,19], axis=0) array(1, 1, 1, 1, 1) >>> np.count_nonzero([0,1,7,0,0],[3,0,0,2,19], axis=1) array(2, 3)

exp(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True, signature, extobj)

Calculate the exponential of all elements in the input array.

Parameters ---------- x : array_like Input values. out : ndarray, None, or tuple of ndarray and None, optional A location into which the result is stored. If provided, it must have a shape that the inputs broadcast to. If not provided or None, a freshly-allocated array is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs. where : array_like, optional This condition is broadcast over the input. At locations where the condition is True, the `out` array will be set to the ufunc result. Elsewhere, the `out` array will retain its original value. Note that if an uninitialized `out` array is created via the default ``out=None``, locations within it where the condition is False will remain uninitialized. **kwargs For other keyword-only arguments, see the :ref:`ufunc docs <ufuncs.kwargs>`.

Returns ------- out : ndarray or scalar Output array, element-wise exponential of `x`. This is a scalar if `x` is a scalar.

See Also -------- expm1 : Calculate ``exp(x) - 1`` for all elements in the array. exp2 : Calculate ``2**x`` for all elements in the array.

Notes ----- The irrational number ``e`` is also known as Euler's number. It is approximately 2.718281, and is the base of the natural logarithm, ``ln`` (this means that, if :math:`x = \ln y = \log_e y`, then :math:`e^x = y`. For real input, ``exp(x)`` is always positive.

For complex arguments, ``x = a + ib``, we can write :math:`e^x = e^a e^b`. The first term, :math:`e^a`, is already known (it is the real argument, described above). The second term, :math:`e^b`, is :math:`\cos b + i \sin b`, a function with magnitude 1 and a periodic phase.

References ---------- .. 1 Wikipedia, 'Exponential function', https://en.wikipedia.org/wiki/Exponential_function .. 2 M. Abramovitz and I. A. Stegun, 'Handbook of Mathematical Functions with Formulas, Graphs, and Mathematical Tables,' Dover, 1964, p. 69, http://www.math.sfu.ca/~cbm/aands/page_69.htm

Examples -------- Plot the magnitude and phase of ``exp(x)`` in the complex plane:

>>> import matplotlib.pyplot as plt

>>> x = np.linspace(-2*np.pi, 2*np.pi, 100) >>> xx = x + 1j * x:, np.newaxis # a + ib over complex plane >>> out = np.exp(xx)

>>> plt.subplot(121) >>> plt.imshow(np.abs(out), ... extent=-2*np.pi, 2*np.pi, -2*np.pi, 2*np.pi, cmap='gray') >>> plt.title('Magnitude of exp(x)')

>>> plt.subplot(122) >>> plt.imshow(np.angle(out), ... extent=-2*np.pi, 2*np.pi, -2*np.pi, 2*np.pi, cmap='hsv') >>> plt.title('Phase (angle) of exp(x)') >>> plt.show()

Find repeats and repeat counts.

Parameters ---------- arr : array_like Input array. This is cast to float64.

Returns ------- values : ndarray The unique values from the (flattened) input that are repeated.

counts : ndarray Number of times the corresponding 'value' is repeated.

Notes ----- In numpy >= 1.9 `numpy.unique` provides similar functionality. The main difference is that `find_repeats` only returns repeated values.

Examples -------- >>> from scipy import stats >>> stats.find_repeats(2, 1, 2, 3, 2, 2, 5) RepeatedResults(values=array(2.), counts=array(4))

>>> stats.find_repeats([10, 20, 1, 2], [5, 5, 4, 4]) RepeatedResults(values=array(4., 5.), counts=array(2, 2))

Perform Fligner-Killeen test for equality of variance.

Fligner's test tests the null hypothesis that all input samples are from populations with equal variances. Fligner-Killeen's test is distribution free when populations are identical 2_.

Parameters ---------- sample1, sample2, ... : array_like Arrays of sample data. Need not be the same length. center : 'mean', 'median', 'trimmed', optional Keyword argument controlling which function of the data is used in computing the test statistic. The default is 'median'. proportiontocut : float, optional When `center` is 'trimmed', this gives the proportion of data points to cut from each end. (See `scipy.stats.trim_mean`.) Default is 0.05.

Returns ------- statistic : float The test statistic. pvalue : float The p-value for the hypothesis test.

See Also -------- bartlett : A parametric test for equality of k variances in normal samples levene : A robust parametric test for equality of k variances

Notes ----- As with Levene's test there are three variants of Fligner's test that differ by the measure of central tendency used in the test. See `levene` for more information.

Conover et al. (1981) examine many of the existing parametric and nonparametric tests by extensive simulations and they conclude that the tests proposed by Fligner and Killeen (1976) and Levene (1960) appear to be superior in terms of robustness of departures from normality and power 3_.

References ---------- .. 1 Park, C. and Lindsay, B. G. (1999). Robust Scale Estimation and Hypothesis Testing based on Quadratic Inference Function. Technical Report #99-03, Center for Likelihood Studies, Pennsylvania State University. https://cecas.clemson.edu/~cspark/cv/paper/qif/draftqif2.pdf

.. 2 Fligner, M.A. and Killeen, T.J. (1976). Distribution-free two-sample tests for scale. 'Journal of the American Statistical Association.' 71(353), 210-213.

.. 3 Park, C. and Lindsay, B. G. (1999). Robust Scale Estimation and Hypothesis Testing based on Quadratic Inference Function. Technical Report #99-03, Center for Likelihood Studies, Pennsylvania State University.

.. 4 Conover, W. J., Johnson, M. E. and Johnson M. M. (1981). A comparative study of tests for homogeneity of variances, with applications to the outer continental shelf biding data. Technometrics, 23(4), 351-361.

floor(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True, signature, extobj)

Return the floor of the input, element-wise.

The floor of the scalar `x` is the largest integer `i`, such that `i <= x`. It is often denoted as :math:`\lfloor x \rfloor`.

Parameters ---------- x : array_like Input data. out : ndarray, None, or tuple of ndarray and None, optional A location into which the result is stored. If provided, it must have a shape that the inputs broadcast to. If not provided or None, a freshly-allocated array is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs. where : array_like, optional This condition is broadcast over the input. At locations where the condition is True, the `out` array will be set to the ufunc result. Elsewhere, the `out` array will retain its original value. Note that if an uninitialized `out` array is created via the default ``out=None``, locations within it where the condition is False will remain uninitialized. **kwargs For other keyword-only arguments, see the :ref:`ufunc docs <ufuncs.kwargs>`.

Returns ------- y : ndarray or scalar The floor of each element in `x`. This is a scalar if `x` is a scalar.

See Also -------- ceil, trunc, rint

Notes ----- Some spreadsheet programs calculate the 'floor-towards-zero', in other words ``floor(-2.5) == -2``. NumPy instead uses the definition of `floor` where `floor(-2.5) == -3`.

Examples -------- >>> a = np.array(-1.7, -1.5, -0.2, 0.2, 1.5, 1.7, 2.0) >>> np.floor(a) array(-2., -2., -1., 0., 1., 1., 2.)

hypot(x1, x2, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True, signature, extobj)

Given the 'legs' of a right triangle, return its hypotenuse.

Equivalent to ``sqrt(x1**2 + x2**2)``, element-wise. If `x1` or `x2` is scalar_like (i.e., unambiguously cast-able to a scalar type), it is broadcast for use with each element of the other argument. (See Examples)

Parameters ---------- x1, x2 : array_like Leg of the triangle(s). If ``x1.shape != x2.shape``, they must be broadcastable to a common shape (which becomes the shape of the output). out : ndarray, None, or tuple of ndarray and None, optional A location into which the result is stored. If provided, it must have a shape that the inputs broadcast to. If not provided or None, a freshly-allocated array is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs. where : array_like, optional This condition is broadcast over the input. At locations where the condition is True, the `out` array will be set to the ufunc result. Elsewhere, the `out` array will retain its original value. Note that if an uninitialized `out` array is created via the default ``out=None``, locations within it where the condition is False will remain uninitialized. **kwargs For other keyword-only arguments, see the :ref:`ufunc docs <ufuncs.kwargs>`.

Returns ------- z : ndarray The hypotenuse of the triangle(s). This is a scalar if both `x1` and `x2` are scalars.

Examples -------- >>> np.hypot(3*np.ones((3, 3)), 4*np.ones((3, 3))) array([ 5., 5., 5.], [ 5., 5., 5.], [ 5., 5., 5.])

Example showing broadcast of scalar_like argument:

>>> np.hypot(3*np.ones((3, 3)), 4) array([ 5., 5., 5.], [ 5., 5., 5.], [ 5., 5., 5.])

Returns True if the type of `element` is a scalar type.

Parameters ---------- element : any Input argument, can be of any type and shape.

Returns ------- val : bool True if `element` is a scalar type, False if it is not.

See Also -------- ndim : Get the number of dimensions of an array

Notes ----- If you need a stricter way to identify a *numerical* scalar, use ``isinstance(x, numbers.Number)``, as that returns ``False`` for most non-numerical elements such as strings.

In most cases ``np.ndim(x) == 0`` should be used instead of this function, as that will also return true for 0d arrays. This is how numpy overloads functions in the style of the ``dx`` arguments to `gradient` and the ``bins`` argument to `histogram`. Some key differences:

+--------------------------------------+---------------+-------------------+ | x |``isscalar(x)``|``np.ndim(x) == 0``| +======================================+===============+===================+ | PEP 3141 numeric objects (including | ``True`` | ``True`` | | builtins) | | | +--------------------------------------+---------------+-------------------+ | builtin string and buffer objects | ``True`` | ``True`` | +--------------------------------------+---------------+-------------------+ | other builtin objects, like | ``False`` | ``True`` | | `pathlib.Path`, `Exception`, | | | | the result of `re.compile` | | | +--------------------------------------+---------------+-------------------+ | third-party objects like | ``False`` | ``True`` | | `matplotlib.figure.Figure` | | | +--------------------------------------+---------------+-------------------+ | zero-dimensional numpy arrays | ``False`` | ``True`` | +--------------------------------------+---------------+-------------------+ | other numpy arrays | ``False`` | ``False`` | +--------------------------------------+---------------+-------------------+ | `list`, `tuple`, and other sequence | ``False`` | ``False`` | | objects | | | +--------------------------------------+---------------+-------------------+

Examples -------- >>> np.isscalar(3.1) True >>> np.isscalar(np.array(3.1)) False >>> np.isscalar(3.1) False >>> np.isscalar(False) True >>> np.isscalar('numpy') True

NumPy supports PEP 3141 numbers:

>>> from fractions import Fraction >>> np.isscalar(Fraction(5, 17)) True >>> from numbers import Number >>> np.isscalar(Number()) True

Return the nth k-statistic (1<=n<=4 so far).

The nth k-statistic k_n is the unique symmetric unbiased estimator of the nth cumulant kappa_n.

Parameters ---------- data : array_like Input array. Note that n-D input gets flattened. n : int,

, 2, 3, 4

, optional Default is equal to 2.

Returns ------- kstat : float The nth k-statistic.

See Also -------- kstatvar: Returns an unbiased estimator of the variance of the k-statistic. moment: Returns the n-th central moment about the mean for a sample.

Notes ----- For a sample size n, the first few k-statistics are given by:

.. math::

k_

= \mu k_

= \fracnn-1 m_

k_

= \frac n^{2

}

(n-1) (n-2) m_

k_

= \frac n^{2 (n + 1)m_{4} - 3(n - 1) m^2_{2}

}

(n-1) (n-2) (n-3)

where :math:`\mu` is the sample mean, :math:`m_2` is the sample variance, and :math:`m_i` is the i-th sample central moment.

References ---------- http://mathworld.wolfram.com/k-Statistic.html

http://mathworld.wolfram.com/Cumulant.html

Examples -------- >>> from scipy import stats >>> rndm = np.random.RandomState(1234)

As sample size increases, n-th moment and n-th k-statistic converge to the same number (although they aren't identical). In the case of the normal distribution, they converge to zero.

>>> for n in 2, 3, 4, 5, 6, 7: ... x = rndm.normal(size=10**n) ... m, k = stats.moment(x, 3), stats.kstat(x, 3) ... print('%.3g %.3g %.3g' % (m, k, m-k)) -0.631 -0.651 0.0194 0.0282 0.0283 -8.49e-05 -0.0454 -0.0454 1.36e-05 7.53e-05 7.53e-05 -2.26e-09 0.00166 0.00166 -4.99e-09 -2.88e-06 -2.88e-06 8.63e-13

Return an unbiased estimator of the variance of the k-statistic.

See `kstat` for more details of the k-statistic.

Parameters ---------- data : array_like Input array. Note that n-D input gets flattened. n : int,

, 2

, optional Default is equal to 2.

Returns ------- kstatvar : float The nth k-statistic variance.

See Also -------- kstat: Returns the n-th k-statistic. moment: Returns the n-th central moment about the mean for a sample.

Notes ----- The variances of the first few k-statistics are given by:

.. math::

var(k_

) = \frac\kappa^2n var(k_

) = \frac\kappa^4n + \frac

\kappa^2_

}

n - 1 var(k_

) = \frac\kappa^6n + \frac

\kappa_2 \kappa_4

n - 1 + \frac

\kappa^2_

}

n - 1 + \frac

n \kappa^3_

}

(n-1) (n-2) var(k_

) = \frac\kappa^8n + \frac

\kappa_2 \kappa_6

n - 1 + \frac

\kappa_

\kappa_5

}

n - 1 + \frac

\kappa^2_

}

n-1 + \frac

n \kappa^2_

\kappa_4

}

(n - 1) (n - 2) + \frac

n \kappa_

\kappa^2_

}

(n - 1) (n - 2) + \frac

(n + 1) n \kappa^4_

}

(n - 1) (n - 2) (n - 3)

Perform Levene test for equal variances.

The Levene test tests the null hypothesis that all input samples are from populations with equal variances. Levene's test is an alternative to Bartlett's test `bartlett` in the case where there are significant deviations from normality.

Parameters ---------- sample1, sample2, ... : array_like The sample data, possibly with different lengths. Only one-dimensional samples are accepted. center : 'mean', 'median', 'trimmed', optional Which function of the data to use in the test. The default is 'median'. proportiontocut : float, optional When `center` is 'trimmed', this gives the proportion of data points to cut from each end. (See `scipy.stats.trim_mean`.) Default is 0.05.

Returns ------- statistic : float The test statistic. pvalue : float The p-value for the test.

Notes ----- Three variations of Levene's test are possible. The possibilities and their recommended usages are:

* 'median' : Recommended for skewed (non-normal) distributions> * 'mean' : Recommended for symmetric, moderate-tailed distributions. * 'trimmed' : Recommended for heavy-tailed distributions.

The test version using the mean was proposed in the original article of Levene (2_) while the median and trimmed mean have been studied by Brown and Forsythe (3_), sometimes also referred to as Brown-Forsythe test.

References ---------- .. 1 https://www.itl.nist.gov/div898/handbook/eda/section3/eda35a.htm .. 2 Levene, H. (1960). In Contributions to Probability and Statistics: Essays in Honor of Harold Hotelling, I. Olkin et al. eds., Stanford University Press, pp. 278-292. .. 3 Brown, M. B. and Forsythe, A. B. (1974), Journal of the American Statistical Association, 69, 364-367

log(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True, signature, extobj)

Natural logarithm, element-wise.

The natural logarithm `log` is the inverse of the exponential function, so that `log(exp(x)) = x`. The natural logarithm is logarithm in base `e`.

Parameters ---------- x : array_like Input value. out : ndarray, None, or tuple of ndarray and None, optional A location into which the result is stored. If provided, it must have a shape that the inputs broadcast to. If not provided or None, a freshly-allocated array is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs. where : array_like, optional This condition is broadcast over the input. At locations where the condition is True, the `out` array will be set to the ufunc result. Elsewhere, the `out` array will retain its original value. Note that if an uninitialized `out` array is created via the default ``out=None``, locations within it where the condition is False will remain uninitialized. **kwargs For other keyword-only arguments, see the :ref:`ufunc docs <ufuncs.kwargs>`.

Returns ------- y : ndarray The natural logarithm of `x`, element-wise. This is a scalar if `x` is a scalar.

See Also -------- log10, log2, log1p, emath.log

Notes ----- Logarithm is a multivalued function: for each `x` there is an infinite number of `z` such that `exp(z) = x`. The convention is to return the `z` whose imaginary part lies in `-pi, pi`.

For real-valued input data types, `log` always returns real output. For each value that cannot be expressed as a real number or infinity, it yields ``nan`` and sets the `invalid` floating point error flag.

For complex-valued input, `log` is a complex analytical function that has a branch cut `-inf, 0` and is continuous from above on it. `log` handles the floating-point negative zero as an infinitesimal negative number, conforming to the C99 standard.

References ---------- .. 1 M. Abramowitz and I.A. Stegun, 'Handbook of Mathematical Functions', 10th printing, 1964, pp. 67. http://www.math.sfu.ca/~cbm/aands/ .. 2 Wikipedia, 'Logarithm'. https://en.wikipedia.org/wiki/Logarithm

Examples -------- >>> np.log(1, np.e, np.e**2, 0) array( 0., 1., 2., -Inf)

Perform a Mood's median test.

Test that two or more samples come from populations with the same median.

Let ``n = len(args)`` be the number of samples. The 'grand median' of all the data is computed, and a contingency table is formed by classifying the values in each sample as being above or below the grand median. The contingency table, along with `correction` and `lambda_`, are passed to `scipy.stats.chi2_contingency` to compute the test statistic and p-value.

Parameters ---------- sample1, sample2, ... : array_like The set of samples. There must be at least two samples. Each sample must be a one-dimensional sequence containing at least one value. The samples are not required to have the same length. ties : str, optional Determines how values equal to the grand median are classified in the contingency table. The string must be one of::

'below': Values equal to the grand median are counted as 'below'. 'above': Values equal to the grand median are counted as 'above'. 'ignore': Values equal to the grand median are not counted.

The default is 'below'. correction : bool, optional If True, *and* there are just two samples, apply Yates' correction for continuity when computing the test statistic associated with the contingency table. Default is True. lambda_ : float or str, optional By default, the statistic computed in this test is Pearson's chi-squared statistic. `lambda_` allows a statistic from the Cressie-Read power divergence family to be used instead. See `power_divergence` for details. Default is 1 (Pearson's chi-squared statistic). nan_policy : 'propagate', 'raise', 'omit', optional Defines how to handle when input contains nan. 'propagate' returns nan, 'raise' throws an error, 'omit' performs the calculations ignoring nan values. Default is 'propagate'.

Returns ------- stat : float The test statistic. The statistic that is returned is determined by `lambda_`. The default is Pearson's chi-squared statistic. p : float The p-value of the test. m : float The grand median. table : ndarray The contingency table. The shape of the table is (2, n), where n is the number of samples. The first row holds the counts of the values above the grand median, and the second row holds the counts of the values below the grand median. The table allows further analysis with, for example, `scipy.stats.chi2_contingency`, or with `scipy.stats.fisher_exact` if there are two samples, without having to recompute the table. If ``nan_policy`` is 'propagate' and there are nans in the input, the return value for ``table`` is ``None``.

See Also -------- kruskal : Compute the Kruskal-Wallis H-test for independent samples. mannwhitneyu : Computes the Mann-Whitney rank test on samples x and y.

Notes ----- .. versionadded:: 0.15.0

References ---------- .. 1 Mood, A. M., Introduction to the Theory of Statistics. McGraw-Hill (1950), pp. 394-399. .. 2 Zar, J. H., Biostatistical Analysis, 5th ed. Prentice Hall (2010). See Sections 8.12 and 10.15.

Examples -------- A biologist runs an experiment in which there are three groups of plants. Group 1 has 16 plants, group 2 has 15 plants, and group 3 has 17 plants. Each plant produces a number of seeds. The seed counts for each group are::

Group 1: 10 14 14 18 20 22 24 25 31 31 32 39 43 43 48 49 Group 2: 28 30 31 33 34 35 36 40 44 55 57 61 91 92 99 Group 3: 0 3 9 22 23 25 25 33 34 34 40 45 46 48 62 67 84

The following code applies Mood's median test to these samples.

>>> g1 = 10, 14, 14, 18, 20, 22, 24, 25, 31, 31, 32, 39, 43, 43, 48, 49 >>> g2 = 28, 30, 31, 33, 34, 35, 36, 40, 44, 55, 57, 61, 91, 92, 99 >>> g3 = 0, 3, 9, 22, 23, 25, 25, 33, 34, 34, 40, 45, 46, 48, 62, 67, 84 >>> from scipy.stats import median_test >>> stat, p, med, tbl = median_test(g1, g2, g3)

The median is

>>> med 34.0

and the contingency table is

>>> tbl array([ 5, 10, 7], [11, 5, 10])

`p` is too large to conclude that the medians are not the same:

>>> p 0.12609082774093244

The 'G-test' can be performed by passing ``lambda_='log-likelihood'`` to `median_test`.

>>> g, p, med, tbl = median_test(g1, g2, g3, lambda_='log-likelihood') >>> p 0.12224779737117837

The median occurs several times in the data, so we'll get a different result if, for example, ``ties='above'`` is used:

>>> stat, p, med, tbl = median_test(g1, g2, g3, ties='above') >>> p 0.063873276069553273

>>> tbl array([ 5, 11, 9], [11, 4, 8])

This example demonstrates that if the data set is not large and there are values equal to the median, the p-value can be sensitive to the choice of `ties`.

Perform Mood's test for equal scale parameters.

Mood's two-sample test for scale parameters is a non-parametric test for the null hypothesis that two samples are drawn from the same distribution with the same scale parameter.

Parameters ---------- x, y : array_like Arrays of sample data. axis : int, optional The axis along which the samples are tested. `x` and `y` can be of different length along `axis`. If `axis` is None, `x` and `y` are flattened and the test is done on all values in the flattened arrays.

Returns ------- z : scalar or ndarray The z-score for the hypothesis test. For 1-D inputs a scalar is returned. p-value : scalar ndarray The p-value for the hypothesis test.

See Also -------- fligner : A non-parametric test for the equality of k variances ansari : A non-parametric test for the equality of 2 variances bartlett : A parametric test for equality of k variances in normal samples levene : A parametric test for equality of k variances

Notes ----- The data are assumed to be drawn from probability distributions ``f(x)`` and ``f(x/s) / s`` respectively, for some probability density function f. The null hypothesis is that ``s == 1``.

For multi-dimensional arrays, if the inputs are of shapes ``(n0, n1, n2, n3)`` and ``(n0, m1, n2, n3)``, then if ``axis=1``, the resulting z and p values will have shape ``(n0, n2, n3)``. Note that ``n1`` and ``m1`` don't have to be equal, but the other dimensions do.

Examples -------- >>> from scipy import stats >>> np.random.seed(1234) >>> x2 = np.random.randn(2, 45, 6, 7) >>> x1 = np.random.randn(2, 30, 6, 7) >>> z, p = stats.mood(x1, x2, axis=1) >>> p.shape (2, 6, 7)

Find the number of points where the difference in scale is not significant:

>>> (p > 0.1).sum() 74

Perform the test with different scales:

>>> x1 = np.random.randn(2, 30) >>> x2 = np.random.randn(2, 35) * 10.0 >>> stats.mood(x1, x2, axis=1) (array(-5.7178125 , -5.25342163), array( 1.07904114e-08, 1.49299218e-07))

'Frozen' distributions for mean, variance, and standard deviation of data.

Parameters ---------- data : array_like Input array. Converted to 1-D using ravel. Requires 2 or more data-points.

Returns ------- mdist : 'frozen' distribution object Distribution object representing the mean of the data. vdist : 'frozen' distribution object Distribution object representing the variance of the data. sdist : 'frozen' distribution object Distribution object representing the standard deviation of the data.

See Also -------- bayes_mvs

Notes ----- The return values from ``bayes_mvs(data)`` is equivalent to ``tuple((x.mean(), x.interval(0.90)) for x in mvsdist(data))``.

In other words, calling ``<dist>.mean()`` and ``<dist>.interval(0.90)`` on the three distribution objects returned from this function will give the same results that are returned from `bayes_mvs`.

References ---------- T.E. Oliphant, 'A Bayesian perspective on estimating mean, variance, and standard-deviation from data', https://scholarsarchive.byu.edu/facpub/278, 2006.

Examples -------- >>> from scipy import stats >>> data = 6, 9, 12, 7, 8, 8, 13 >>> mean, var, std = stats.mvsdist(data)

We now have frozen distribution objects 'mean', 'var' and 'std' that we can examine:

>>> mean.mean() 9.0 >>> mean.interval(0.95) (6.6120585482655692, 11.387941451734431) >>> mean.std() 1.1952286093343936

Returns a new subclass of tuple with named fields.

>>> Point = namedtuple('Point', 'x', 'y') >>> Point.__doc__ # docstring for the new class 'Point(x, y)' >>> p = Point(11, y=22) # instantiate with positional args or keywords >>> p0 + p1 # indexable like a plain tuple 33 >>> x, y = p # unpack like a regular tuple >>> x, y (11, 22) >>> p.x + p.y # fields also accessible by name 33 >>> d = p._asdict() # convert to a dictionary >>> d'x' 11 >>> Point( **d) # convert from a dictionary Point(x=11, y=22) >>> p._replace(x=100) # _replace() is like str.replace() but targets named fields Point(x=100, y=22)

Calculate the shape parameter that maximizes the PPCC.

The probability plot correlation coefficient (PPCC) plot can be used to determine the optimal shape parameter for a one-parameter family of distributions. ppcc_max returns the shape parameter that would maximize the probability plot correlation coefficient for the given data to a one-parameter family of distributions.

Parameters ---------- x : array_like Input array. brack : tuple, optional Triple (a,b,c) where (a<b<c). If bracket consists of two numbers (a, c) then they are assumed to be a starting interval for a downhill bracket search (see `scipy.optimize.brent`). dist : str or stats.distributions instance, optional Distribution or distribution function name. Objects that look enough like a stats.distributions instance (i.e. they have a ``ppf`` method) are also accepted. The default is ``'tukeylambda'``.

Returns ------- shape_value : float The shape parameter at which the probability plot correlation coefficient reaches its max value.

See Also -------- ppcc_plot, probplot, boxcox

Notes ----- The brack keyword serves as a starting point which is useful in corner cases. One can use a plot to obtain a rough visual estimate of the location for the maximum to start the search near it.

References ---------- .. 1 J.J. Filliben, 'The Probability Plot Correlation Coefficient Test for Normality', Technometrics, Vol. 17, pp. 111-117, 1975.

.. 2 https://www.itl.nist.gov/div898/handbook/eda/section3/ppccplot.htm

Examples -------- First we generate some random data from a Tukey-Lambda distribution, with shape parameter -0.7:

>>> from scipy import stats >>> x = stats.tukeylambda.rvs(-0.7, loc=2, scale=0.5, size=10000, ... random_state=1234567) + 1e4

Now we explore this data with a PPCC plot as well as the related probability plot and Box-Cox normplot. A red line is drawn where we expect the PPCC value to be maximal (at the shape parameter -0.7 used above):

>>> import matplotlib.pyplot as plt >>> fig = plt.figure(figsize=(8, 6)) >>> ax = fig.add_subplot(111) >>> res = stats.ppcc_plot(x, -5, 5, plot=ax)

We calculate the value where the shape should reach its maximum and a red line is drawn there. The line should coincide with the highest point in the ppcc_plot.

>>> max = stats.ppcc_max(x) >>> ax.vlines(max, 0, 1, colors='r', label='Expected shape value')

>>> plt.show()

Calculate and optionally plot probability plot correlation coefficient.

The probability plot correlation coefficient (PPCC) plot can be used to determine the optimal shape parameter for a one-parameter family of distributions. It cannot be used for distributions without shape parameters (like the normal distribution) or with multiple shape parameters.

By default a Tukey-Lambda distribution (`stats.tukeylambda`) is used. A Tukey-Lambda PPCC plot interpolates from long-tailed to short-tailed distributions via an approximately normal one, and is therefore particularly useful in practice.

Parameters ---------- x : array_like Input array. a, b : scalar Lower and upper bounds of the shape parameter to use. dist : str or stats.distributions instance, optional Distribution or distribution function name. Objects that look enough like a stats.distributions instance (i.e. they have a ``ppf`` method) are also accepted. The default is ``'tukeylambda'``. plot : object, optional If given, plots PPCC against the shape parameter. `plot` is an object that has to have methods 'plot' and 'text'. The `matplotlib.pyplot` module or a Matplotlib Axes object can be used, or a custom object with the same methods. Default is None, which means that no plot is created. N : int, optional Number of points on the horizontal axis (equally distributed from `a` to `b`).

Returns ------- svals : ndarray The shape values for which `ppcc` was calculated. ppcc : ndarray The calculated probability plot correlation coefficient values.

See Also -------- ppcc_max, probplot, boxcox_normplot, tukeylambda

References ---------- J.J. Filliben, 'The Probability Plot Correlation Coefficient Test for Normality', Technometrics, Vol. 17, pp. 111-117, 1975.

Examples -------- First we generate some random data from a Tukey-Lambda distribution, with shape parameter -0.7:

>>> from scipy import stats >>> import matplotlib.pyplot as plt >>> np.random.seed(1234567) >>> x = stats.tukeylambda.rvs(-0.7, loc=2, scale=0.5, size=10000) + 1e4

Now we explore this data with a PPCC plot as well as the related probability plot and Box-Cox normplot. A red line is drawn where we expect the PPCC value to be maximal (at the shape parameter -0.7 used above):

>>> fig = plt.figure(figsize=(12, 4)) >>> ax1 = fig.add_subplot(131) >>> ax2 = fig.add_subplot(132) >>> ax3 = fig.add_subplot(133) >>> res = stats.probplot(x, plot=ax1) >>> res = stats.boxcox_normplot(x, -5, 5, plot=ax2) >>> res = stats.ppcc_plot(x, -5, 5, plot=ax3) >>> ax3.vlines(-0.7, 0, 1, colors='r', label='Expected shape value') >>> plt.show()

Calculate quantiles for a probability plot, and optionally show the plot.

Generates a probability plot of sample data against the quantiles of a specified theoretical distribution (the normal distribution by default). `probplot` optionally calculates a best-fit line for the data and plots the results using Matplotlib or a given plot function.

Parameters ---------- x : array_like Sample/response data from which `probplot` creates the plot. sparams : tuple, optional Distribution-specific shape parameters (shape parameters plus location and scale). dist : str or stats.distributions instance, optional Distribution or distribution function name. The default is 'norm' for a normal probability plot. Objects that look enough like a stats.distributions instance (i.e. they have a ``ppf`` method) are also accepted. fit : bool, optional Fit a least-squares regression (best-fit) line to the sample data if True (default). plot : object, optional If given, plots the quantiles and least squares fit. `plot` is an object that has to have methods 'plot' and 'text'. The `matplotlib.pyplot` module or a Matplotlib Axes object can be used, or a custom object with the same methods. Default is None, which means that no plot is created.

Returns ------- (osm, osr) : tuple of ndarrays Tuple of theoretical quantiles (osm, or order statistic medians) and ordered responses (osr). `osr` is simply sorted input `x`. For details on how `osm` is calculated see the Notes section. (slope, intercept, r) : tuple of floats, optional Tuple containing the result of the least-squares fit, if that is performed by `probplot`. `r` is the square root of the coefficient of determination. If ``fit=False`` and ``plot=None``, this tuple is not returned.

Notes ----- Even if `plot` is given, the figure is not shown or saved by `probplot`; ``plt.show()`` or ``plt.savefig('figname.png')`` should be used after calling `probplot`.

`probplot` generates a probability plot, which should not be confused with a Q-Q or a P-P plot. Statsmodels has more extensive functionality of this type, see ``statsmodels.api.ProbPlot``.

The formula used for the theoretical quantiles (horizontal axis of the probability plot) is Filliben's estimate::

quantiles = dist.ppf(val), for

0.5**(1/n), for i = n val = (i - 0.3175) / (n + 0.365), for i = 2, ..., n-1 1 - 0.5**(1/n), for i = 1

where ``i`` indicates the i-th ordered value and ``n`` is the total number of values.

Examples -------- >>> from scipy import stats >>> import matplotlib.pyplot as plt >>> nsample = 100 >>> np.random.seed(7654321)

A t distribution with small degrees of freedom:

>>> ax1 = plt.subplot(221) >>> x = stats.t.rvs(3, size=nsample) >>> res = stats.probplot(x, plot=plt)

A t distribution with larger degrees of freedom:

>>> ax2 = plt.subplot(222) >>> x = stats.t.rvs(25, size=nsample) >>> res = stats.probplot(x, plot=plt)

A mixture of two normal distributions with broadcasting:

>>> ax3 = plt.subplot(223) >>> x = stats.norm.rvs(loc=0,5, scale=1,1.5, ... size=(nsample//2,2)).ravel() >>> res = stats.probplot(x, plot=plt)

A standard normal distribution:

>>> ax4 = plt.subplot(224) >>> x = stats.norm.rvs(loc=0, scale=1, size=nsample) >>> res = stats.probplot(x, plot=plt)

Produce a new figure with a loggamma distribution, using the ``dist`` and ``sparams`` keywords:

>>> fig = plt.figure() >>> ax = fig.add_subplot(111) >>> x = stats.loggamma.rvs(c=2.5, size=500) >>> res = stats.probplot(x, dist=stats.loggamma, sparams=(2.5,), plot=ax) >>> ax.set_title('Probplot for loggamma dist with shape parameter 2.5')

Show the results with Matplotlib:

>>> plt.show()

Return a contiguous flattened array.

A 1-D array, containing the elements of the input, is returned. A copy is made only if needed.

As of NumPy 1.10, the returned array will have the same type as the input array. (for example, a masked array will be returned for a masked array input)

Parameters ---------- a : array_like Input array. The elements in `a` are read in the order specified by `order`, and packed as a 1-D array. order : 'C','F', 'A', 'K', optional

The elements of `a` are read using this index order. 'C' means to index the elements in row-major, C-style order, with the last axis index changing fastest, back to the first axis index changing slowest. 'F' means to index the elements in column-major, Fortran-style order, with the first index changing fastest, and the last index changing slowest. Note that the 'C' and 'F' options take no account of the memory layout of the underlying array, and only refer to the order of axis indexing. 'A' means to read the elements in Fortran-like index order if `a` is Fortran *contiguous* in memory, C-like order otherwise. 'K' means to read the elements in the order they occur in memory, except for reversing the data when strides are negative. By default, 'C' index order is used.

Returns ------- y : array_like y is an array of the same subtype as `a`, with shape ``(a.size,)``. Note that matrices are special cased for backward compatibility, if `a` is a matrix, then y is a 1-D ndarray.

See Also -------- ndarray.flat : 1-D iterator over an array. ndarray.flatten : 1-D array copy of the elements of an array in row-major order. ndarray.reshape : Change the shape of an array without changing its data.

Notes ----- In row-major, C-style order, in two dimensions, the row index varies the slowest, and the column index the quickest. This can be generalized to multiple dimensions, where row-major order implies that the index along the first axis varies slowest, and the index along the last quickest. The opposite holds for column-major, Fortran-style index ordering.

When a view is desired in as many cases as possible, ``arr.reshape(-1)`` may be preferable.

Examples -------- It is equivalent to ``reshape(-1, order=order)``.

>>> x = np.array([1, 2, 3], [4, 5, 6]) >>> np.ravel(x) array(1, 2, 3, 4, 5, 6)

>>> x.reshape(-1) array(1, 2, 3, 4, 5, 6)

>>> np.ravel(x, order='F') array(1, 4, 2, 5, 3, 6)

When ``order`` is 'A', it will preserve the array's 'C' or 'F' ordering:

>>> np.ravel(x.T) array(1, 4, 2, 5, 3, 6) >>> np.ravel(x.T, order='A') array(1, 2, 3, 4, 5, 6)

When ``order`` is 'K', it will preserve orderings that are neither 'C' nor 'F', but won't reverse axes:

>>> a = np.arange(3)::-1; a array(2, 1, 0) >>> a.ravel(order='C') array(2, 1, 0) >>> a.ravel(order='K') array(2, 1, 0)

>>> a = np.arange(12).reshape(2,3,2).swapaxes(1,2); a array([[ 0, 2, 4], [ 1, 3, 5]], [[ 6, 8, 10], [ 7, 9, 11]]) >>> a.ravel(order='C') array( 0, 2, 4, 1, 3, 5, 6, 8, 10, 7, 9, 11) >>> a.ravel(order='K') array( 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11)

Perform the Shapiro-Wilk test for normality.

The Shapiro-Wilk test tests the null hypothesis that the data was drawn from a normal distribution.

Parameters ---------- x : array_like Array of sample data.

Returns ------- W : float The test statistic. p-value : float The p-value for the hypothesis test.

See Also -------- anderson : The Anderson-Darling test for normality kstest : The Kolmogorov-Smirnov test for goodness of fit.

Notes ----- The algorithm used is described in 4_ but censoring parameters as described are not implemented. For N > 5000 the W test statistic is accurate but the p-value may not be.

The chance of rejecting the null hypothesis when it is true is close to 5% regardless of sample size.

References ---------- .. 1 https://www.itl.nist.gov/div898/handbook/prc/section2/prc213.htm .. 2 Shapiro, S. S. & Wilk, M.B (1965). An analysis of variance test for normality (complete samples), Biometrika, Vol. 52, pp. 591-611. .. 3 Razali, N. M. & Wah, Y. B. (2011) Power comparisons of Shapiro-Wilk, Kolmogorov-Smirnov, Lilliefors and Anderson-Darling tests, Journal of Statistical Modeling and Analytics, Vol. 2, pp. 21-33. .. 4 ALGORITHM AS R94 APPL. STATIST. (1995) VOL. 44, NO. 4.

Examples -------- >>> from scipy import stats >>> np.random.seed(12345678) >>> x = stats.norm.rvs(loc=5, scale=3, size=100) >>> stats.shapiro(x) (0.9772805571556091, 0.08144091814756393)

sin(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True, signature, extobj)

Trigonometric sine, element-wise.

Parameters ---------- x : array_like Angle, in radians (:math:`2 \pi` rad equals 360 degrees). out : ndarray, None, or tuple of ndarray and None, optional A location into which the result is stored. If provided, it must have a shape that the inputs broadcast to. If not provided or None, a freshly-allocated array is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs. where : array_like, optional This condition is broadcast over the input. At locations where the condition is True, the `out` array will be set to the ufunc result. Elsewhere, the `out` array will retain its original value. Note that if an uninitialized `out` array is created via the default ``out=None``, locations within it where the condition is False will remain uninitialized. **kwargs For other keyword-only arguments, see the :ref:`ufunc docs <ufuncs.kwargs>`.

Returns ------- y : array_like The sine of each element of x. This is a scalar if `x` is a scalar.

See Also -------- arcsin, sinh, cos

Notes ----- The sine is one of the fundamental functions of trigonometry (the mathematical study of triangles). Consider a circle of radius 1 centered on the origin. A ray comes in from the :math:`+x` axis, makes an angle at the origin (measured counter-clockwise from that axis), and departs from the origin. The :math:`y` coordinate of the outgoing ray's intersection with the unit circle is the sine of that angle. It ranges from -1 for :math:`x=3\pi / 2` to +1 for :math:`\pi / 2.` The function has zeroes where the angle is a multiple of :math:`\pi`. Sines of angles between :math:`\pi` and :math:`2\pi` are negative. The numerous properties of the sine and related functions are included in any standard trigonometry text.

Examples -------- Print sine of one angle:

>>> np.sin(np.pi/2.) 1.0

Print sines of an array of angles given in degrees:

>>> np.sin(np.array((0., 30., 45., 60., 90.)) * np.pi / 180. ) array( 0. , 0.5 , 0.70710678, 0.8660254 , 1. )

Plot the sine function:

>>> import matplotlib.pylab as plt >>> x = np.linspace(-np.pi, np.pi, 201) >>> plt.plot(x, np.sin(x)) >>> plt.xlabel('Angle rad') >>> plt.ylabel('sin(x)') >>> plt.axis('tight') >>> plt.show()

Return a sorted copy of an array.

Parameters ---------- a : array_like Array to be sorted. axis : int or None, optional Axis along which to sort. If None, the array is flattened before sorting. The default is -1, which sorts along the last axis. kind : 'quicksort', 'mergesort', 'heapsort', 'stable', optional Sorting algorithm. The default is 'quicksort'. Note that both 'stable' and 'mergesort' use timsort or radix sort under the covers and, in general, the actual implementation will vary with data type. The 'mergesort' option is retained for backwards compatibility.

.. versionchanged:: 1.15.0. The 'stable' option was added.

order : str or list of str, optional When `a` is an array with fields defined, this argument specifies which fields to compare first, second, etc. A single field can be specified as a string, and not all fields need be specified, but unspecified fields will still be used, in the order in which they come up in the dtype, to break ties.

Returns ------- sorted_array : ndarray Array of the same type and shape as `a`.

See Also -------- ndarray.sort : Method to sort an array in-place. argsort : Indirect sort. lexsort : Indirect stable sort on multiple keys. searchsorted : Find elements in a sorted array. partition : Partial sort.

Notes ----- The various sorting algorithms are characterized by their average speed, worst case performance, work space size, and whether they are stable. A stable sort keeps items with the same key in the same relative order. The four algorithms implemented in NumPy have the following properties:

=========== ======= ============= ============ ======== kind speed worst case work space stable =========== ======= ============= ============ ======== 'quicksort' 1 O(n^2) 0 no 'heapsort' 3 O(n*log(n)) 0 no 'mergesort' 2 O(n*log(n)) ~n/2 yes 'timsort' 2 O(n*log(n)) ~n/2 yes =========== ======= ============= ============ ========

.. note:: The datatype determines which of 'mergesort' or 'timsort' is actually used, even if 'mergesort' is specified. User selection at a finer scale is not currently available.

All the sort algorithms make temporary copies of the data when sorting along any but the last axis. Consequently, sorting along the last axis is faster and uses less space than sorting along any other axis.

The sort order for complex numbers is lexicographic. If both the real and imaginary parts are non-nan then the order is determined by the real parts except when they are equal, in which case the order is determined by the imaginary parts.

Previous to numpy 1.4.0 sorting real and complex arrays containing nan values led to undefined behaviour. In numpy versions >= 1.4.0 nan values are sorted to the end. The extended sort order is:

* Real: R, nan * Complex: R + Rj, R + nanj, nan + Rj, nan + nanj

where R is a non-nan real value. Complex values with the same nan placements are sorted according to the non-nan part if it exists. Non-nan values are sorted as before.

.. versionadded:: 1.12.0

quicksort has been changed to `introsort <https://en.wikipedia.org/wiki/Introsort>`_. When sorting does not make enough progress it switches to `heapsort <https://en.wikipedia.org/wiki/Heapsort>`_. This implementation makes quicksort O(n*log(n)) in the worst case.

'stable' automatically chooses the best stable sorting algorithm for the data type being sorted. It, along with 'mergesort' is currently mapped to `timsort <https://en.wikipedia.org/wiki/Timsort>`_ or `radix sort <https://en.wikipedia.org/wiki/Radix_sort>`_ depending on the data type. API forward compatibility currently limits the ability to select the implementation and it is hardwired for the different data types.

.. versionadded:: 1.17.0

Timsort is added for better performance on already or nearly sorted data. On random data timsort is almost identical to mergesort. It is now used for stable sort while quicksort is still the default sort if none is chosen. For timsort details, refer to `CPython listsort.txt <https://github.com/python/cpython/blob/3.7/Objects/listsort.txt>`_. 'mergesort' and 'stable' are mapped to radix sort for integer data types. Radix sort is an O(n) sort instead of O(n log n).

.. versionchanged:: 1.17.0

NaT now sorts to the end of arrays for consistency with NaN.

Examples -------- >>> a = np.array([1,4],[3,1]) >>> np.sort(a) # sort along the last axis array([1, 4], [1, 3]) >>> np.sort(a, axis=None) # sort the flattened array array(1, 1, 3, 4) >>> np.sort(a, axis=0) # sort along the first axis array([1, 1], [3, 4])

Use the `order` keyword to specify a field to use when sorting a structured array:

>>> dtype = ('name', 'S10'), ('height', float), ('age', int) >>> values = ('Arthur', 1.8, 41), ('Lancelot', 1.9, 38), ... ('Galahad', 1.7, 38) >>> a = np.array(values, dtype=dtype) # create a structured array >>> np.sort(a, order='height') # doctest: +SKIP array(('Galahad', 1.7, 38), ('Arthur', 1.8, 41), ('Lancelot', 1.8999999999999999, 38), dtype=('name', '|S10'), ('height', '<f8'), ('age', '<i4'))

Sort by age, then height if ages are equal:

>>> np.sort(a, order='age', 'height') # doctest: +SKIP array(('Galahad', 1.7, 38), ('Lancelot', 1.8999999999999999, 38), ('Arthur', 1.8, 41), dtype=('name', '|S10'), ('height', '<f8'), ('age', '<i4'))

sqrt(x, /, out=None, *, where=True, casting='same_kind', order='K', dtype=None, subok=True, signature, extobj)

Return the non-negative square-root of an array, element-wise.

Parameters ---------- x : array_like The values whose square-roots are required. out : ndarray, None, or tuple of ndarray and None, optional A location into which the result is stored. If provided, it must have a shape that the inputs broadcast to. If not provided or None, a freshly-allocated array is returned. A tuple (possible only as a keyword argument) must have length equal to the number of outputs. where : array_like, optional This condition is broadcast over the input. At locations where the condition is True, the `out` array will be set to the ufunc result. Elsewhere, the `out` array will retain its original value. Note that if an uninitialized `out` array is created via the default ``out=None``, locations within it where the condition is False will remain uninitialized. **kwargs For other keyword-only arguments, see the :ref:`ufunc docs <ufuncs.kwargs>`.

Returns ------- y : ndarray An array of the same shape as `x`, containing the positive square-root of each element in `x`. If any element in `x` is complex, a complex array is returned (and the square-roots of negative reals are calculated). If all of the elements in `x` are real, so is `y`, with negative elements returning ``nan``. If `out` was provided, `y` is a reference to it. This is a scalar if `x` is a scalar.

See Also -------- lib.scimath.sqrt A version which returns complex numbers when given negative reals.

Notes ----- *sqrt* has--consistent with common convention--as its branch cut the real 'interval' `-inf`, 0), and is continuous from above on it. A branch cut is a curve in the complex plane across which a given complex function fails to be continuous. Examples -------- >>> np.sqrt([1,4,9]) array([ 1., 2., 3.]) >>> np.sqrt([4, -1, -3+4J]) array([ 2.+0.j, 0.+1.j, 1.+2.j]) >>> np.sqrt([4, -1, np.inf]) array([ 2., nan, inf])

Find the unique elements of an array.

Returns the sorted unique elements of an array. There are three optional outputs in addition to the unique elements:

* the indices of the input array that give the unique values * the indices of the unique array that reconstruct the input array * the number of times each unique value comes up in the input array

Parameters ---------- ar : array_like Input array. Unless `axis` is specified, this will be flattened if it is not already 1-D. return_index : bool, optional If True, also return the indices of `ar` (along the specified axis, if provided, or in the flattened array) that result in the unique array. return_inverse : bool, optional If True, also return the indices of the unique array (for the specified axis, if provided) that can be used to reconstruct `ar`. return_counts : bool, optional If True, also return the number of times each unique item appears in `ar`.

.. versionadded:: 1.9.0

axis : int or None, optional The axis to operate on. If None, `ar` will be flattened. If an integer, the subarrays indexed by the given axis will be flattened and treated as the elements of a 1-D array with the dimension of the given axis, see the notes for more details. Object arrays or structured arrays that contain objects are not supported if the `axis` kwarg is used. The default is None.

.. versionadded:: 1.13.0

Returns ------- unique : ndarray The sorted unique values. unique_indices : ndarray, optional The indices of the first occurrences of the unique values in the original array. Only provided if `return_index` is True. unique_inverse : ndarray, optional The indices to reconstruct the original array from the unique array. Only provided if `return_inverse` is True. unique_counts : ndarray, optional The number of times each of the unique values comes up in the original array. Only provided if `return_counts` is True.

.. versionadded:: 1.9.0

See Also -------- numpy.lib.arraysetops : Module with a number of other functions for performing set operations on arrays.

Notes ----- When an axis is specified the subarrays indexed by the axis are sorted. This is done by making the specified axis the first dimension of the array (move the axis to the first dimension to keep the order of the other axes) and then flattening the subarrays in C order. The flattened subarrays are then viewed as a structured type with each element given a label, with the effect that we end up with a 1-D array of structured types that can be treated in the same way as any other 1-D array. The result is that the flattened subarrays are sorted in lexicographic order starting with the first element.

Examples -------- >>> np.unique(1, 1, 2, 2, 3, 3) array(1, 2, 3) >>> a = np.array([1, 1], [2, 3]) >>> np.unique(a) array(1, 2, 3)

Return the unique rows of a 2D array

>>> a = np.array([1, 0, 0], [1, 0, 0], [2, 3, 4]) >>> np.unique(a, axis=0) array([1, 0, 0], [2, 3, 4])

Return the indices of the original array that give the unique values:

>>> a = np.array('a', 'b', 'b', 'c', 'a') >>> u, indices = np.unique(a, return_index=True) >>> u array('a', 'b', 'c', dtype='<U1') >>> indices array(0, 1, 3) >>> aindices array('a', 'b', 'c', dtype='<U1')

Reconstruct the input array from the unique values:

>>> a = np.array(1, 2, 6, 4, 2, 3, 2) >>> u, indices = np.unique(a, return_inverse=True) >>> u array(1, 2, 3, 4, 6) >>> indices array(0, 1, 4, ..., 1, 2, 1) >>> uindices array(1, 2, 6, ..., 2, 3, 2)

Calculate the Wilcoxon signed-rank test.

The Wilcoxon signed-rank test tests the null hypothesis that two related paired samples come from the same distribution. In particular, it tests whether the distribution of the differences x - y is symmetric about zero. It is a non-parametric version of the paired T-test.

Parameters ---------- x : array_like Either the first set of measurements (in which case `y` is the second set of measurements), or the differences between two sets of measurements (in which case `y` is not to be specified.) Must be one-dimensional. y : array_like, optional Either the second set of measurements (if `x` is the first set of measurements), or not specified (if `x` is the differences between two sets of measurements.) Must be one-dimensional. zero_method : 'pratt', 'wilcox', 'zsplit', optional The following options are available (default is 'wilcox'):

* 'pratt': Includes zero-differences in the ranking process, but drops the ranks of the zeros, see 4_, (more conservative). * 'wilcox': Discards all zero-differences, the default. * 'zsplit': Includes zero-differences in the ranking process and split the zero rank between positive and negative ones. correction : bool, optional If True, apply continuity correction by adjusting the Wilcoxon rank statistic by 0.5 towards the mean value when computing the z-statistic. Default is False. alternative : 'two-sided', 'greater', 'less', optional The alternative hypothesis to be tested, see Notes. Default is 'two-sided'.

Returns ------- statistic : float If `alternative` is 'two-sided', the sum of the ranks of the differences above or below zero, whichever is smaller. Otherwise the sum of the ranks of the differences above zero. pvalue : float The p-value for the test depending on `alternative`.

See Also -------- kruskal, mannwhitneyu

Notes ----- The test has been introduced in 4_. Given n independent samples (xi, yi) from a bivariate distribution (i.e. paired samples), it computes the differences di = xi - yi. One assumption of the test is that the differences are symmetric, see 2_. The two-sided test has the null hypothesis that the median of the differences is zero against the alternative that it is different from zero. The one-sided test has the null hypothesis that the median is positive against the alternative that it is negative (``alternative == 'less'``), or vice versa (``alternative == 'greater.'``).

The test uses a normal approximation to derive the p-value (if ``zero_method == 'pratt'``, the approximation is adjusted as in 5_). A typical rule is to require that n > 20 (2_, p. 383). For smaller n, exact tables can be used to find critical values.

References ---------- .. 1 https://en.wikipedia.org/wiki/Wilcoxon_signed-rank_test .. 2 Conover, W.J., Practical Nonparametric Statistics, 1971. .. 3 Pratt, J.W., Remarks on Zeros and Ties in the Wilcoxon Signed Rank Procedures, Journal of the American Statistical Association, Vol. 54, 1959, pp. 655-667. :doi:`10.1080/01621459.1959.10501526` .. 4 Wilcoxon, F., Individual Comparisons by Ranking Methods, Biometrics Bulletin, Vol. 1, 1945, pp. 80-83. :doi:`10.2307/3001968` .. 5 Cureton, E.E., The Normal Approximation to the Signed-Rank Sampling Distribution When Zero Differences are Present, Journal of the American Statistical Association, Vol. 62, 1967, pp. 1068-1069. :doi:`10.1080/01621459.1967.10500917`

Examples -------- In 4_, the differences in height between cross- and self-fertilized corn plants is given as follows:

>>> d = 6, 8, 14, 16, 23, 24, 28, 29, 41, -48, 49, 56, 60, -67, 75

Cross-fertilized plants appear to be be higher. To test the null hypothesis that there is no height difference, we can apply the two-sided test:

>>> from scipy.stats import wilcoxon >>> w, p = wilcoxon(d) >>> w, p (24.0, 0.04088813291185591)

Hence, we would reject the null hypothesis at a confidence level of 5%, concluding that there is a difference in height between the groups. To confirm that the median of the differences can be assumed to be positive, we use:

>>> w, p = wilcoxon(d, alternative='greater') >>> w, p (96.0, 0.020444066455927955)

This shows that the null hypothesis that the median is negative can be rejected at a confidence level of 5% in favor of the alternative that the median is greater than zero. The p-value based on the approximation is within the range of 0.019 and 0.054 given in 2_. Note that the statistic changed to 96 in the one-sided case (the sum of ranks of positive differences) whereas it is 24 in the two-sided case (the minimum of sum of ranks above and below zero).

Return a dataset transformed by a Yeo-Johnson power transformation.

Parameters ---------- x : ndarray Input array. Should be 1-dimensional. lmbda : float, optional If ``lmbda`` is ``None``, find the lambda that maximizes the log-likelihood function and return it as the second output argument. Otherwise the transformation is done for the given value.

Returns ------- yeojohnson: ndarray Yeo-Johnson power transformed array. maxlog : float, optional If the `lmbda` parameter is None, the second returned argument is the lambda that maximizes the log-likelihood function.

See Also -------- probplot, yeojohnson_normplot, yeojohnson_normmax, yeojohnson_llf, boxcox

Notes ----- The Yeo-Johnson transform is given by::

y = ((x + 1)**lmbda - 1) / lmbda, for x >= 0, lmbda != 0 log(x + 1), for x >= 0, lmbda = 0 -((-x + 1)**(2 - lmbda) - 1) / (2 - lmbda), for x < 0, lmbda != 2 -log(-x + 1), for x < 0, lmbda = 2

Unlike `boxcox`, `yeojohnson` does not require the input data to be positive.

.. versionadded:: 1.2.0

References ---------- I. Yeo and R.A. Johnson, 'A New Family of Power Transformations to Improve Normality or Symmetry', Biometrika 87.4 (2000):

Examples -------- >>> from scipy import stats >>> import matplotlib.pyplot as plt

We generate some random variates from a non-normal distribution and make a probability plot for it, to show it is non-normal in the tails:

>>> fig = plt.figure() >>> ax1 = fig.add_subplot(211) >>> x = stats.loggamma.rvs(5, size=500) + 5 >>> prob = stats.probplot(x, dist=stats.norm, plot=ax1) >>> ax1.set_xlabel('') >>> ax1.set_title('Probplot against normal distribution')

We now use `yeojohnson` to transform the data so it's closest to normal:

>>> ax2 = fig.add_subplot(212) >>> xt, lmbda = stats.yeojohnson(x) >>> prob = stats.probplot(xt, dist=stats.norm, plot=ax2) >>> ax2.set_title('Probplot after Yeo-Johnson transformation')

>>> plt.show()

The yeojohnson log-likelihood function.

Parameters ---------- lmb : scalar Parameter for Yeo-Johnson transformation. See `yeojohnson` for details. data : array_like Data to calculate Yeo-Johnson log-likelihood for. If `data` is multi-dimensional, the log-likelihood is calculated along the first axis.

Returns ------- llf : float Yeo-Johnson log-likelihood of `data` given `lmb`.

See Also -------- yeojohnson, probplot, yeojohnson_normplot, yeojohnson_normmax

Notes ----- The Yeo-Johnson log-likelihood function is defined here as

.. math::

llf = N/2 \log(\hat\sigma^2) + (\lambda - 1) \sum_i \text sign (x_i)\log(|x_i| + 1)

where :math:`\hat\sigma^2` is estimated variance of the the Yeo-Johnson transformed input data ``x``.

.. versionadded:: 1.2.0

Examples -------- >>> from scipy import stats >>> import matplotlib.pyplot as plt >>> from mpl_toolkits.axes_grid1.inset_locator import inset_axes >>> np.random.seed(1245)

Generate some random variates and calculate Yeo-Johnson log-likelihood values for them for a range of ``lmbda`` values:

>>> x = stats.loggamma.rvs(5, loc=10, size=1000) >>> lmbdas = np.linspace(-2, 10) >>> llf = np.zeros(lmbdas.shape, dtype=float) >>> for ii, lmbda in enumerate(lmbdas): ... llfii = stats.yeojohnson_llf(lmbda, x)

Also find the optimal lmbda value with `yeojohnson`:

>>> x_most_normal, lmbda_optimal = stats.yeojohnson(x)

Plot the log-likelihood as function of lmbda. Add the optimal lmbda as a horizontal line to check that that's really the optimum:

>>> fig = plt.figure() >>> ax = fig.add_subplot(111) >>> ax.plot(lmbdas, llf, 'b.-') >>> ax.axhline(stats.yeojohnson_llf(lmbda_optimal, x), color='r') >>> ax.set_xlabel('lmbda parameter') >>> ax.set_ylabel('Yeo-Johnson log-likelihood')

Now add some probability plots to show that where the log-likelihood is maximized the data transformed with `yeojohnson` looks closest to normal:

>>> locs = 3, 10, 4 # 'lower left', 'center', 'lower right' >>> for lmbda, loc in zip(-1, lmbda_optimal, 9, locs): ... xt = stats.yeojohnson(x, lmbda=lmbda) ... (osm, osr), (slope, intercept, r_sq) = stats.probplot(xt) ... ax_inset = inset_axes(ax, width='20%', height='20%', loc=loc) ... ax_inset.plot(osm, osr, 'c.', osm, slope*osm + intercept, 'k-') ... ax_inset.set_xticklabels() ... ax_inset.set_yticklabels() ... ax_inset.set_title(r'$\lambda=%1.2f$' % lmbda)

>>> plt.show()

Compute optimal Yeo-Johnson transform parameter.

Compute optimal Yeo-Johnson transform parameter for input data, using maximum likelihood estimation.

Parameters ---------- x : array_like Input array. brack : 2-tuple, optional The starting interval for a downhill bracket search with `optimize.brent`. Note that this is in most cases not critical; the final result is allowed to be outside this bracket.

Returns ------- maxlog : float The optimal transform parameter found.

See Also -------- yeojohnson, yeojohnson_llf, yeojohnson_normplot

Notes ----- .. versionadded:: 1.2.0

Examples -------- >>> from scipy import stats >>> import matplotlib.pyplot as plt >>> np.random.seed(1234) # make this example reproducible

Generate some data and determine optimal ``lmbda``

>>> x = stats.loggamma.rvs(5, size=30) + 5 >>> lmax = stats.yeojohnson_normmax(x)

>>> fig = plt.figure() >>> ax = fig.add_subplot(111) >>> prob = stats.yeojohnson_normplot(x, -10, 10, plot=ax) >>> ax.axvline(lmax, color='r')

>>> plt.show()

Compute parameters for a Yeo-Johnson normality plot, optionally show it.

A Yeo-Johnson normality plot shows graphically what the best transformation parameter is to use in `yeojohnson` to obtain a distribution that is close to normal.

Parameters ---------- x : array_like Input array. la, lb : scalar The lower and upper bounds for the ``lmbda`` values to pass to `yeojohnson` for Yeo-Johnson transformations. These are also the limits of the horizontal axis of the plot if that is generated. plot : object, optional If given, plots the quantiles and least squares fit. `plot` is an object that has to have methods 'plot' and 'text'. The `matplotlib.pyplot` module or a Matplotlib Axes object can be used, or a custom object with the same methods. Default is None, which means that no plot is created. N : int, optional Number of points on the horizontal axis (equally distributed from `la` to `lb`).

Returns ------- lmbdas : ndarray The ``lmbda`` values for which a Yeo-Johnson transform was done. ppcc : ndarray Probability Plot Correlelation Coefficient, as obtained from `probplot` when fitting the Box-Cox transformed input `x` against a normal distribution.

See Also -------- probplot, yeojohnson, yeojohnson_normmax, yeojohnson_llf, ppcc_max

Notes ----- Even if `plot` is given, the figure is not shown or saved by `boxcox_normplot`; ``plt.show()`` or ``plt.savefig('figname.png')`` should be used after calling `probplot`.

.. versionadded:: 1.2.0

Examples -------- >>> from scipy import stats >>> import matplotlib.pyplot as plt

Generate some non-normally distributed data, and create a Yeo-Johnson plot:

>>> x = stats.loggamma.rvs(5, size=500) + 5 >>> fig = plt.figure() >>> ax = fig.add_subplot(111) >>> prob = stats.yeojohnson_normplot(x, -20, 20, plot=ax)

Determine and plot the optimal ``lmbda`` to transform ``x`` and plot it in the same plot:

>>> _, maxlog = stats.yeojohnson(x) >>> ax.axvline(maxlog, color='r')

>>> plt.show()

zeros(shape, dtype=float, order='C')

Return a new array of given shape and type, filled with zeros.

Parameters ---------- shape : int or tuple of ints Shape of the new array, e.g., ``(2, 3)`` or ``2``. dtype : data-type, optional The desired data-type for the array, e.g., `numpy.int8`. Default is `numpy.float64`. order : 'C', 'F', optional, default: 'C' Whether to store multi-dimensional data in row-major (C-style) or column-major (Fortran-style) order in memory.

Returns ------- out : ndarray Array of zeros with the given shape, dtype, and order.

See Also -------- zeros_like : Return an array of zeros with shape and type of input. empty : Return a new uninitialized array. ones : Return a new array setting values to one. full : Return a new array of given shape filled with value.

Examples -------- >>> np.zeros(5) array( 0., 0., 0., 0., 0.)

>>> np.zeros((5,), dtype=int) array(0, 0, 0, 0, 0)

>>> np.zeros((2, 1)) array([ 0.], [ 0.])

>>> s = (2,2) >>> np.zeros(s) array([ 0., 0.], [ 0., 0.])

>>> np.zeros((2,), dtype=('x', 'i4'), ('y', 'i4')) # custom dtype array((0, 0), (0, 0), dtype=('x', '<i4'), ('y', '<i4'))