package np

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

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

Add arguments element-wise.

Parameters ---------- x1, x2 : array_like The arrays to be added. 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 ------- add : ndarray or scalar The sum of `x1` and `x2`, element-wise. This is a scalar if both `x1` and `x2` are scalars.

Notes ----- Equivalent to `x1` + `x2` in terms of array broadcasting.

Examples -------- >>> np.add(1.0, 4.0) 5.0 >>> x1 = np.arange(9.0).reshape((3, 3)) >>> x2 = np.arange(3.0) >>> np.add(x1, x2) array([ 0., 2., 4.], [ 3., 5., 7.], [ 6., 8., 10.])

Apply a function to 1-D slices along the given axis.

Execute `func1d(a, *args)` where `func1d` operates on 1-D arrays and `a` is a 1-D slice of `arr` along `axis`.

This is equivalent to (but faster than) the following use of `ndindex` and `s_`, which sets each of ``ii``, ``jj``, and ``kk`` to a tuple of indices::

Ni, Nk = a.shape:axis, a.shapeaxis+1: for ii in ndindex(Ni): for kk in ndindex(Nk): f = func1d(arrii + s_[:,] + kk) Nj = f.shape for jj in ndindex(Nj): outii + jj + kk = fjj

Equivalently, eliminating the inner loop, this can be expressed as::

Ni, Nk = a.shape:axis, a.shapeaxis+1: for ii in ndindex(Ni): for kk in ndindex(Nk): outii + s_[...,] + kk = func1d(arrii + s_[:,] + kk)

Parameters ---------- func1d : function (M,) -> (Nj...) This function should accept 1-D arrays. It is applied to 1-D slices of `arr` along the specified axis. axis : integer Axis along which `arr` is sliced. arr : ndarray (Ni..., M, Nk...) Input array. args : any Additional arguments to `func1d`. kwargs : any Additional named arguments to `func1d`.

.. versionadded:: 1.9.0

Returns ------- out : ndarray (Ni..., Nj..., Nk...) The output array. The shape of `out` is identical to the shape of `arr`, except along the `axis` dimension. This axis is removed, and replaced with new dimensions equal to the shape of the return value of `func1d`. So if `func1d` returns a scalar `out` will have one fewer dimensions than `arr`.

See Also -------- apply_over_axes : Apply a function repeatedly over multiple axes.

Examples -------- >>> def my_func(a): ... '''Average first and last element of a 1-D array''' ... return (a0 + a-1) * 0.5 >>> b = np.array([1,2,3], [4,5,6], [7,8,9]) >>> np.apply_along_axis(my_func, 0, b) array(4., 5., 6.) >>> np.apply_along_axis(my_func, 1, b) array(2., 5., 8.)

For a function that returns a 1D array, the number of dimensions in `outarr` is the same as `arr`.

>>> b = np.array([8,1,7], [4,3,9], [5,2,6]) >>> np.apply_along_axis(sorted, 1, b) array([1, 7, 8], [3, 4, 9], [2, 5, 6])

For a function that returns a higher dimensional array, those dimensions are inserted in place of the `axis` dimension.

>>> b = np.array([1,2,3], [4,5,6], [7,8,9]) >>> np.apply_along_axis(np.diag, -1, b) array([[1, 0, 0], [0, 2, 0], [0, 0, 3]], [[4, 0, 0], [0, 5, 0], [0, 0, 6]], [[7, 0, 0], [0, 8, 0], [0, 0, 9]])

Apply a function repeatedly over multiple axes.

`func` is called as `res = func(a, axis)`, where `axis` is the first element of `axes`. The result `res` of the function call must have either the same dimensions as `a` or one less dimension. If `res` has one less dimension than `a`, a dimension is inserted before `axis`. The call to `func` is then repeated for each axis in `axes`, with `res` as the first argument.

Parameters ---------- func : function This function must take two arguments, `func(a, axis)`. a : array_like Input array. axes : array_like Axes over which `func` is applied; the elements must be integers.

Returns ------- apply_over_axis : ndarray The output array. The number of dimensions is the same as `a`, but the shape can be different. This depends on whether `func` changes the shape of its output with respect to its input.

See Also -------- apply_along_axis : Apply a function to 1-D slices of an array along the given axis.

Examples -------- >>> a = np.ma.arange(24).reshape(2,3,4) >>> a:,0,1 = np.ma.masked >>> a:,1,: = np.ma.masked >>> a masked_array( data=[[0, --, 2, 3], [--, --, --, --], [8, 9, 10, 11]], [[12, --, 14, 15], [--, --, --, --], [20, 21, 22, 23]], mask=[[False, True, False, False], [ True, True, True, True], [False, False, False, False]], [[False, True, False, False], [ True, True, True, True], [False, False, False, False]], fill_value=999999) >>> np.ma.apply_over_axes(np.ma.sum, a, 0,2) masked_array( data=[[46], [--], [124]], mask=[[False], [ True], [False]], fill_value=999999)

Tuple axis arguments to ufuncs are equivalent:

>>> np.ma.sum(a, axis=(0,2)).reshape((1,-1,1)) masked_array( data=[[46], [--], [124]], mask=[[False], [ True], [False]], fill_value=999999)

An array class with possibly masked values.

Masked values of True exclude the corresponding element from any computation.

Construction::

x = MaskedArray(data, mask=nomask, dtype=None, copy=False, subok=True, ndmin=0, fill_value=None, keep_mask=True, hard_mask=None, shrink=True, order=None)

Parameters ---------- data : array_like Input data. mask : sequence, optional Mask. Must be convertible to an array of booleans with the same shape as `data`. True indicates a masked (i.e. invalid) data. dtype : dtype, optional Data type of the output. If `dtype` is None, the type of the data argument (``data.dtype``) is used. If `dtype` is not None and different from ``data.dtype``, a copy is performed. copy : bool, optional Whether to copy the input data (True), or to use a reference instead. Default is False. subok : bool, optional Whether to return a subclass of `MaskedArray` if possible (True) or a plain `MaskedArray`. Default is True. ndmin : int, optional Minimum number of dimensions. Default is 0. fill_value : scalar, optional Value used to fill in the masked values when necessary. If None, a default based on the data-type is used. keep_mask : bool, optional Whether to combine `mask` with the mask of the input data, if any (True), or to use only `mask` for the output (False). Default is True. hard_mask : bool, optional Whether to use a hard mask or not. With a hard mask, masked values cannot be unmasked. Default is False. shrink : bool, optional Whether to force compression of an empty mask. Default is True. order : 'C', 'F', 'A', optional Specify the order of the array. If order is 'C', then the array will be in C-contiguous order (last-index varies the fastest). If order is 'F', then the returned array will be in Fortran-contiguous order (first-index varies the fastest). If order is 'A' (default), then the returned array may be in any order (either C-, Fortran-contiguous, or even discontiguous), unless a copy is required, in which case it will be C-contiguous.

Convert the input to a masked array of the given data-type.

No copy is performed if the input is already an `ndarray`. If `a` is a subclass of `MaskedArray`, a base class `MaskedArray` is returned.

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

Returns ------- out : MaskedArray Masked array interpretation of `a`.

See Also -------- asanyarray : Similar to `asarray`, but conserves subclasses.

Examples -------- >>> x = np.arange(10.).reshape(2, 5) >>> x array([0., 1., 2., 3., 4.], [5., 6., 7., 8., 9.]) >>> np.ma.asarray(x) masked_array( data=[0., 1., 2., 3., 4.], [5., 6., 7., 8., 9.], mask=False, fill_value=1e+20) >>> type(np.ma.asarray(x)) <class 'numpy.ma.core.MaskedArray'>

atleast_1d( *args, **kwargs)

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])

Notes ----- The function is applied to both the _data and the _mask, if any.

atleast_2d( *args, **kwargs)

View inputs as arrays with at least two dimensions.

Parameters ---------- arys1, arys2, ... : array_like One or more array-like sequences. Non-array inputs are converted to arrays. Arrays that already have two or more dimensions are preserved.

Returns ------- res, res2, ... : ndarray An array, or list of arrays, each with ``a.ndim >= 2``. Copies are avoided where possible, and views with two or more dimensions are returned.

See Also -------- atleast_1d, atleast_3d

Examples -------- >>> np.atleast_2d(3.0) array([3.])

>>> x = np.arange(3.0) >>> np.atleast_2d(x) array([0., 1., 2.]) >>> np.atleast_2d(x).base is x True

>>> np.atleast_2d(1, 1, 2, [1, 2]) array([[1]]), array([[1, 2]]), array([[1, 2]])

Notes ----- The function is applied to both the _data and the _mask, if any.

atleast_3d( *args, **kwargs)

View inputs as arrays with at least three dimensions.

Parameters ---------- arys1, arys2, ... : array_like One or more array-like sequences. Non-array inputs are converted to arrays. Arrays that already have three or more dimensions are preserved.

Returns ------- res1, res2, ... : ndarray An array, or list of arrays, each with ``a.ndim >= 3``. Copies are avoided where possible, and views with three or more dimensions are returned. For example, a 1-D array of shape ``(N,)`` becomes a view of shape ``(1, N, 1)``, and a 2-D array of shape ``(M, N)`` becomes a view of shape ``(M, N, 1)``.

See Also -------- atleast_1d, atleast_2d

Examples -------- >>> np.atleast_3d(3.0) array([[3.]])

>>> x = np.arange(3.0) >>> np.atleast_3d(x).shape (1, 3, 1)

>>> x = np.arange(12.0).reshape(4,3) >>> np.atleast_3d(x).shape (4, 3, 1) >>> np.atleast_3d(x).base is x.base # x is a reshape, so not base itself True

>>> for arr in np.atleast_3d(1, 2, [1, 2], [[1, 2]]): ... print(arr, arr.shape) # doctest: +SKIP ... [[1] [2]] (1, 2, 1) [[1] [2]] (1, 2, 1) [[1 2]] (1, 1, 2)

Notes ----- The function is applied to both the _data and the _mask, if any.

Return the weighted average of array over the given axis.

Parameters ---------- a : array_like Data to be averaged. Masked entries are not taken into account in the computation. axis : int, optional Axis along which to average `a`. If None, averaging is done over the flattened array. weights : array_like, optional The importance that each element has in the computation of the average. The weights array can either be 1-D (in which case its length must be the size of `a` along the given axis) or of the same shape as `a`. If ``weights=None``, then all data in `a` are assumed to have a weight equal to one. The 1-D calculation is::

avg = sum(a * weights) / sum(weights)

The only constraint on `weights` is that `sum(weights)` must not be 0. returned : bool, optional Flag indicating whether a tuple ``(result, sum of weights)`` should be returned as output (True), or just the result (False). Default is False.

Returns ------- average, sum_of_weights : (tuple of) scalar or MaskedArray The average along the specified axis. When returned is `True`, return a tuple with the average as the first element and the sum of the weights as the second element. The return type is `np.float64` if `a` is of integer type and floats smaller than `float64`, or the input data-type, otherwise. If returned, `sum_of_weights` is always `float64`.

Examples -------- >>> a = np.ma.array(1., 2., 3., 4., mask=False, False, True, True) >>> np.ma.average(a, weights=3, 1, 0, 0) 1.25

>>> x = np.ma.arange(6.).reshape(3, 2) >>> x masked_array( data=[0., 1.], [2., 3.], [4., 5.], mask=False, fill_value=1e+20) >>> avg, sumweights = np.ma.average(x, axis=0, weights=1, 2, 3, ... returned=True) >>> avg masked_array(data=2.6666666666666665, 3.6666666666666665, mask=False, False, fill_value=1e+20)

Returns a list of slices corresponding to the masked clumps of a 1-D array. (A 'clump' is defined as a contiguous region of the array).

Parameters ---------- a : ndarray A one-dimensional masked array.

Returns ------- slices : list of slice The list of slices, one for each continuous region of masked elements in `a`.

Notes ----- .. versionadded:: 1.4.0

See Also -------- flatnotmasked_edges, flatnotmasked_contiguous, notmasked_edges notmasked_contiguous, clump_unmasked

Examples -------- >>> a = np.ma.masked_array(np.arange(10)) >>> a[0, 1, 2, 6, 8, 9] = np.ma.masked >>> np.ma.clump_masked(a) slice(0, 3, None), slice(6, 7, None), slice(8, 10, None)

Return list of slices corresponding to the unmasked clumps of a 1-D array. (A 'clump' is defined as a contiguous region of the array).

Parameters ---------- a : ndarray A one-dimensional masked array.

Returns ------- slices : list of slice The list of slices, one for each continuous region of unmasked elements in `a`.

Notes ----- .. versionadded:: 1.4.0

See Also -------- flatnotmasked_edges, flatnotmasked_contiguous, notmasked_edges notmasked_contiguous, clump_masked

Examples -------- >>> a = np.ma.masked_array(np.arange(10)) >>> a[0, 1, 2, 6, 8, 9] = np.ma.masked >>> np.ma.clump_unmasked(a) slice(3, 6, None), slice(7, 8, None)

column_stack( *args, **kwargs)

Stack 1-D arrays as columns into a 2-D array.

Take a sequence of 1-D arrays and stack them as columns to make a single 2-D array. 2-D arrays are stacked as-is, just like with `hstack`. 1-D arrays are turned into 2-D columns first.

Parameters ---------- tup : sequence of 1-D or 2-D arrays. Arrays to stack. All of them must have the same first dimension.

Returns ------- stacked : 2-D array The array formed by stacking the given arrays.

See Also -------- stack, hstack, vstack, concatenate

Examples -------- >>> a = np.array((1,2,3)) >>> b = np.array((2,3,4)) >>> np.column_stack((a,b)) array([1, 2], [2, 3], [3, 4])

Notes ----- The function is applied to both the _data and the _mask, if any.

Suppress whole columns of a 2-D array that contain masked values.

This is equivalent to ``np.ma.compress_rowcols(a, 1)``, see `extras.compress_rowcols` for details.

See Also -------- extras.compress_rowcols

Suppress slices from multiple dimensions which contain masked values.

Parameters ---------- x : array_like, MaskedArray The array to operate on. If not a MaskedArray instance (or if no array elements are masked, `x` is interpreted as a MaskedArray with `mask` set to `nomask`. axis : tuple of ints or int, optional Which dimensions to suppress slices from can be configured with this parameter.

• If axis is a tuple of ints, those are the axes to suppress slices from.
• If axis is an int, then that is the only axis to suppress slices from.
• If axis is None, all axis are selected.

Returns ------- compress_array : ndarray The compressed array.

Suppress the rows and/or columns of a 2-D array that contain masked values.

The suppression behavior is selected with the `axis` parameter.

• If axis is None, both rows and columns are suppressed.
• If axis is 0, only rows are suppressed.
• If axis is 1 or -1, only columns are suppressed.

Parameters ---------- x : array_like, MaskedArray The array to operate on. If not a MaskedArray instance (or if no array elements are masked), `x` is interpreted as a MaskedArray with `mask` set to `nomask`. Must be a 2D array. axis : int, optional Axis along which to perform the operation. Default is None.

Returns ------- compressed_array : ndarray The compressed array.

Examples -------- >>> x = np.ma.array(np.arange(9).reshape(3, 3), mask=[1, 0, 0], ... [1, 0, 0], ... [0, 0, 0]) >>> x masked_array( data=[--, 1, 2], [--, 4, 5], [6, 7, 8], mask=[ True, False, False], [ True, False, False], [False, False, False], fill_value=999999)

>>> np.ma.compress_rowcols(x) array([7, 8]) >>> np.ma.compress_rowcols(x, 0) array([6, 7, 8]) >>> np.ma.compress_rowcols(x, 1) array([1, 2], [4, 5], [7, 8])

Suppress whole rows of a 2-D array that contain masked values.

This is equivalent to ``np.ma.compress_rowcols(a, 0)``, see `extras.compress_rowcols` for details.

See Also -------- extras.compress_rowcols

Concatenate a sequence of arrays along the given axis.

Parameters ---------- arrays : sequence of array_like The arrays must have the same shape, except in the dimension corresponding to `axis` (the first, by default). axis : int, optional The axis along which the arrays will be joined. Default is 0.

Returns ------- result : MaskedArray The concatenated array with any masked entries preserved.

See Also -------- numpy.concatenate : Equivalent function in the top-level NumPy module.

Examples -------- >>> import numpy.ma as ma >>> a = ma.arange(3) >>> a1 = ma.masked >>> b = ma.arange(2, 5) >>> a masked_array(data=0, --, 2, mask=False, True, False, fill_value=999999) >>> b masked_array(data=2, 3, 4, mask=False, fill_value=999999) >>> ma.concatenate(a, b) masked_array(data=0, --, 2, 2, 3, 4, mask=False, True, False, False, False, False, fill_value=999999)

Return Pearson product-moment correlation coefficients.

Except for the handling of missing data this function does the same as `numpy.corrcoef`. For more details and examples, see `numpy.corrcoef`.

Parameters ---------- x : array_like A 1-D or 2-D array containing multiple variables and observations. Each row of `x` represents a variable, and each column a single observation of all those variables. Also see `rowvar` below. y : array_like, optional An additional set of variables and observations. `y` has the same shape as `x`. rowvar : bool, optional If `rowvar` is True (default), then each row represents a variable, with observations in the columns. Otherwise, the relationship is transposed: each column represents a variable, while the rows contain observations. bias : _NoValue, optional Has no effect, do not use.

.. deprecated:: 1.10.0 allow_masked : bool, optional If True, masked values are propagated pair-wise: if a value is masked in `x`, the corresponding value is masked in `y`. If False, raises an exception. Because `bias` is deprecated, this argument needs to be treated as keyword only to avoid a warning. ddof : _NoValue, optional Has no effect, do not use.

.. deprecated:: 1.10.0

See Also -------- numpy.corrcoef : Equivalent function in top-level NumPy module. cov : Estimate the covariance matrix.

Notes ----- This function accepts but discards arguments `bias` and `ddof`. This is for backwards compatibility with previous versions of this function. These arguments had no effect on the return values of the function and can be safely ignored in this and previous versions of numpy.

count(self, axis=None, keepdims=<no value>)

Count the non-masked elements of the array along the given axis.

Parameters ---------- axis : None or int or tuple of ints, optional Axis or axes along which the count is performed. The default, None, performs the count 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:: 1.10.0

If this is a tuple of ints, the count is performed on multiple axes, instead of a single axis or all the axes as before. 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 array.

Returns ------- result : ndarray or scalar An array with the same shape as the input array, with the specified axis removed. If the array is a 0-d array, or if `axis` is None, a scalar is returned.

See Also -------- count_masked : Count masked elements in array or along a given axis.

Examples -------- >>> import numpy.ma as ma >>> a = ma.arange(6).reshape((2, 3)) >>> a1, : = ma.masked >>> a masked_array( data=[0, 1, 2], [--, --, --], mask=[False, False, False], [ True, True, True], fill_value=999999) >>> a.count() 3

When the `axis` keyword is specified an array of appropriate size is returned.

>>> a.count(axis=0) array(1, 1, 1) >>> a.count(axis=1) array(3, 0)

Count the number of masked elements along the given axis.

Parameters ---------- arr : array_like An array with (possibly) masked elements. axis : int, optional Axis along which to count. If None (default), a flattened version of the array is used.

Returns ------- count : int, ndarray The total number of masked elements (axis=None) or the number of masked elements along each slice of the given axis.

See Also -------- MaskedArray.count : Count non-masked elements.

Examples -------- >>> import numpy.ma as ma >>> a = np.arange(9).reshape((3,3)) >>> a = ma.array(a) >>> a1, 0 = ma.masked >>> a1, 2 = ma.masked >>> a2, 1 = ma.masked >>> a masked_array( data=[0, 1, 2], [--, 4, --], [6, --, 8], mask=[False, False, False], [ True, False, True], [False, True, False], fill_value=999999) >>> ma.count_masked(a) 3

When the `axis` keyword is used an array is returned.

>>> ma.count_masked(a, axis=0) array(1, 1, 1) >>> ma.count_masked(a, axis=1) array(0, 2, 1)

Estimate the covariance matrix.

Except for the handling of missing data this function does the same as `numpy.cov`. For more details and examples, see `numpy.cov`.

By default, masked values are recognized as such. If `x` and `y` have the same shape, a common mask is allocated: if ``xi,j`` is masked, then ``yi,j`` will also be masked. Setting `allow_masked` to False will raise an exception if values are missing in either of the input arrays.

Parameters ---------- x : array_like A 1-D or 2-D array containing multiple variables and observations. Each row of `x` represents a variable, and each column a single observation of all those variables. Also see `rowvar` below. y : array_like, optional An additional set of variables and observations. `y` has the same form as `x`. rowvar : bool, optional If `rowvar` is True (default), then each row represents a variable, with observations in the columns. Otherwise, the relationship is transposed: each column represents a variable, while the rows contain observations. bias : bool, optional Default normalization (False) is by ``(N-1)``, where ``N`` is the number of observations given (unbiased estimate). If `bias` is True, then normalization is by ``N``. This keyword can be overridden by the keyword ``ddof`` in numpy versions >= 1.5. allow_masked : bool, optional If True, masked values are propagated pair-wise: if a value is masked in `x`, the corresponding value is masked in `y`. If False, raises a `ValueError` exception when some values are missing. ddof : None, int, optional If not ``None`` normalization is by ``(N - ddof)``, where ``N`` is the number of observations; this overrides the value implied by ``bias``. The default value is ``None``.

.. versionadded:: 1.5

Raises ------ ValueError Raised if some values are missing and `allow_masked` is False.

See Also -------- numpy.cov

diagflat( *args, **kwargs)

Create a two-dimensional array with the flattened input as a diagonal.

Parameters ---------- v : array_like Input data, which is flattened and set as the `k`-th diagonal of the output. k : int, optional Diagonal to set; 0, the default, corresponds to the 'main' diagonal, a positive (negative) `k` giving the number of the diagonal above (below) the main.

Returns ------- out : ndarray The 2-D output array.

See Also -------- diag : MATLAB work-alike for 1-D and 2-D arrays. diagonal : Return specified diagonals. trace : Sum along diagonals.

Examples -------- >>> np.diagflat([1,2], [3,4]) array([1, 0, 0, 0], [0, 2, 0, 0], [0, 0, 3, 0], [0, 0, 0, 4])

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

Notes ----- The function is applied to both the _data and the _mask, if any.

Return the dot product of two arrays.

This function is the equivalent of `numpy.dot` that takes masked values into account. Note that `strict` and `out` are in different position than in the method version. In order to maintain compatibility with the corresponding method, it is recommended that the optional arguments be treated as keyword only. At some point that may be mandatory.

.. note:: Works only with 2-D arrays at the moment.

Parameters ---------- a, b : masked_array_like Inputs arrays. strict : bool, optional Whether masked data are propagated (True) or set to 0 (False) for the computation. Default is False. Propagating the mask means that if a masked value appears in a row or column, the whole row or column is considered masked. out : masked_array, optional Output argument. This must have the exact kind that would be returned if it was not used. In particular, it must have the right type, must be C-contiguous, and its dtype must be the dtype that would be returned for `dot(a,b)`. This is a performance feature. Therefore, if these conditions are not met, an exception is raised, instead of attempting to be flexible.

.. versionadded:: 1.10.2

See Also -------- numpy.dot : Equivalent function for ndarrays.

Examples -------- >>> a = np.ma.array([1, 2, 3], [4, 5, 6], mask=[1, 0, 0], [0, 0, 0]) >>> b = np.ma.array([1, 2], [3, 4], [5, 6], mask=[1, 0], [0, 0], [0, 0]) >>> np.ma.dot(a, b) masked_array( data=[21, 26], [45, 64], mask=[False, False], [False, False], fill_value=999999) >>> np.ma.dot(a, b, strict=True) masked_array( data=[--, --], [--, 64], mask=[ True, True], [ True, False], fill_value=999999)

dstack( *args, **kwargs)

Stack arrays in sequence depth wise (along third axis).

This is equivalent to concatenation along the third axis after 2-D arrays of shape `(M,N)` have been reshaped to `(M,N,1)` and 1-D arrays of shape `(N,)` have been reshaped to `(1,N,1)`. Rebuilds arrays divided by `dsplit`.

This function makes most sense for arrays with up to 3 dimensions. For instance, for pixel-data with a height (first axis), width (second axis), and r/g/b channels (third axis). The functions `concatenate`, `stack` and `block` provide more general stacking and concatenation operations.

Parameters ---------- tup : sequence of arrays The arrays must have the same shape along all but the third axis. 1-D or 2-D arrays must have the same shape.

Returns ------- stacked : ndarray The array formed by stacking the given arrays, will be at least 3-D.

See Also -------- stack : Join a sequence of arrays along a new axis. vstack : Stack along first axis. hstack : Stack along second axis. concatenate : Join a sequence of arrays along an existing axis. dsplit : Split array along third axis.

Examples -------- >>> a = np.array((1,2,3)) >>> b = np.array((2,3,4)) >>> np.dstack((a,b)) array([[1, 2], [2, 3], [3, 4]])

>>> a = np.array([1],[2],[3]) >>> b = np.array([2],[3],[4]) >>> np.dstack((a,b)) array([[1, 2]], [[2, 3]], [[3, 4]])

Notes ----- The function is applied to both the _data and the _mask, if any.

Compute the differences between consecutive elements of an array.

This function is the equivalent of `numpy.ediff1d` that takes masked values into account, see `numpy.ediff1d` for details.

See Also -------- numpy.ediff1d : Equivalent function for ndarrays.

Return input as an array with masked data replaced by a fill value.

If `a` is not a `MaskedArray`, `a` itself is returned. If `a` is a `MaskedArray` and `fill_value` is None, `fill_value` is set to ``a.fill_value``.

Parameters ---------- a : MaskedArray or array_like An input object. fill_value : array_like, optional. Can be scalar or non-scalar. If non-scalar, the resulting filled array should be broadcastable over input array. Default is None.

Returns ------- a : ndarray The filled array.

See Also -------- compressed

Examples -------- >>> x = np.ma.array(np.arange(9).reshape(3, 3), mask=[1, 0, 0], ... [1, 0, 0], ... [0, 0, 0]) >>> x.filled() array([999999, 1, 2], [999999, 4, 5], [ 6, 7, 8]) >>> x.filled(fill_value=333) array([333, 1, 2], [333, 4, 5], [ 6, 7, 8]) >>> x.filled(fill_value=np.arange(3)) array([0, 1, 2], [0, 4, 5], [6, 7, 8])

Find contiguous unmasked data in a masked array along the given axis.

Parameters ---------- a : narray The input array.

Returns ------- slice_list : list A sorted sequence of `slice` objects (start index, end index).

..versionchanged:: 1.15.0 Now returns an empty list instead of None for a fully masked array

See Also -------- flatnotmasked_edges, notmasked_contiguous, notmasked_edges clump_masked, clump_unmasked

Notes ----- Only accepts 2-D arrays at most.

Examples -------- >>> a = np.ma.arange(10) >>> np.ma.flatnotmasked_contiguous(a) slice(0, 10, None)

>>> mask = (a < 3) | (a > 8) | (a == 5) >>> amask = np.ma.masked >>> np.array(a~a.mask) array(3, 4, 6, 7, 8)

>>> np.ma.flatnotmasked_contiguous(a) slice(3, 5, None), slice(6, 9, None) >>> a: = np.ma.masked >>> np.ma.flatnotmasked_contiguous(a)

Find the indices of the first and last unmasked values.

Expects a 1-D `MaskedArray`, returns None if all values are masked.

Parameters ---------- a : array_like Input 1-D `MaskedArray`

Returns ------- edges : ndarray or None The indices of first and last non-masked value in the array. Returns None if all values are masked.

See Also -------- flatnotmasked_contiguous, notmasked_contiguous, notmasked_edges clump_masked, clump_unmasked

Notes ----- Only accepts 1-D arrays.

Examples -------- >>> a = np.ma.arange(10) >>> np.ma.flatnotmasked_edges(a) array(0, 9)

>>> mask = (a < 3) | (a > 8) | (a == 5) >>> amask = np.ma.masked >>> np.array(a~a.mask) array(3, 4, 6, 7, 8)

>>> np.ma.flatnotmasked_edges(a) array(3, 8)

>>> a: = np.ma.masked >>> print(np.ma.flatnotmasked_edges(a)) None

Flatten a sequence in place.

Return the youngest subclass of MaskedArray from a list of (masked) arrays.

In case of siblings, the first listed takes over.

Return the data of a masked array as an ndarray.

Return the data of `a` (if any) as an ndarray if `a` is a ``MaskedArray``, else return `a` as a ndarray or subclass (depending on `subok`) if not.

Parameters ---------- a : array_like Input ``MaskedArray``, alternatively a ndarray or a subclass thereof. subok : bool Whether to force the output to be a `pure` ndarray (False) or to return a subclass of ndarray if appropriate (True, default).

See Also -------- getmask : Return the mask of a masked array, or nomask. getmaskarray : Return the mask of a masked array, or full array of False.

Examples -------- >>> import numpy.ma as ma >>> a = ma.masked_equal([1,2],[3,4], 2) >>> a masked_array( data=[1, --], [3, 4], mask=[False, True], [False, False], fill_value=2) >>> ma.getdata(a) array([1, 2], [3, 4])

Equivalently use the ``MaskedArray`` `data` attribute.

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

Return the mask of a masked array, or nomask.

Return the mask of `a` as an ndarray if `a` is a `MaskedArray` and the mask is not `nomask`, else return `nomask`. To guarantee a full array of booleans of the same shape as a, use `getmaskarray`.

Parameters ---------- a : array_like Input `MaskedArray` for which the mask is required.

See Also -------- getdata : Return the data of a masked array as an ndarray. getmaskarray : Return the mask of a masked array, or full array of False.

Examples -------- >>> import numpy.ma as ma >>> a = ma.masked_equal([1,2],[3,4], 2) >>> a masked_array( data=[1, --], [3, 4], mask=[False, True], [False, False], fill_value=2) >>> ma.getmask(a) array([False, True], [False, False])

Equivalently use the `MaskedArray` `mask` attribute.

>>> a.mask array([False, True], [False, False])

Result when mask == `nomask`

>>> b = ma.masked_array([1,2],[3,4]) >>> b masked_array( data=[1, 2], [3, 4], mask=False, fill_value=999999) >>> ma.nomask False >>> ma.getmask(b) == ma.nomask True >>> b.mask == ma.nomask True

Return the mask of a masked array, or full boolean array of False.

Return the mask of `arr` as an ndarray if `arr` is a `MaskedArray` and the mask is not `nomask`, else return a full boolean array of False of the same shape as `arr`.

Parameters ---------- arr : array_like Input `MaskedArray` for which the mask is required.

See Also -------- getmask : Return the mask of a masked array, or nomask. getdata : Return the data of a masked array as an ndarray.

Examples -------- >>> import numpy.ma as ma >>> a = ma.masked_equal([1,2],[3,4], 2) >>> a masked_array( data=[1, --], [3, 4], mask=[False, True], [False, False], fill_value=2) >>> ma.getmaskarray(a) array([False, True], [False, False])

Result when mask == ``nomask``

>>> b = ma.masked_array([1,2],[3,4]) >>> b masked_array( data=[1, 2], [3, 4], mask=False, fill_value=999999) >>> ma.getmaskarray(b) array([False, False], [False, False])

hsplit( *args, **kwargs)

Split an array into multiple sub-arrays horizontally (column-wise).

Please refer to the `split` documentation. `hsplit` is equivalent to `split` with ``axis=1``, the array is always split along the second axis regardless of the array dimension.

See Also -------- split : Split an array into multiple sub-arrays of equal size.

Examples -------- >>> x = np.arange(16.0).reshape(4, 4) >>> x array([ 0., 1., 2., 3.], [ 4., 5., 6., 7.], [ 8., 9., 10., 11.], [12., 13., 14., 15.]) >>> np.hsplit(x, 2) array([[ 0., 1.], [ 4., 5.], [ 8., 9.], [12., 13.]]), array([[ 2., 3.], [ 6., 7.], [10., 11.], [14., 15.]]) >>> np.hsplit(x, np.array(3, 6)) array([[ 0., 1., 2.], [ 4., 5., 6.], [ 8., 9., 10.], [12., 13., 14.]]), array([[ 3.], [ 7.], [11.], [15.]]), array([], shape=(4, 0), dtype=float64)

With a higher dimensional array the split is still along the second axis.

>>> x = np.arange(8.0).reshape(2, 2, 2) >>> x array([[0., 1.], [2., 3.]], [[4., 5.], [6., 7.]]) >>> np.hsplit(x, 2) array([[[0., 1.]], [[4., 5.]]]), array([[[2., 3.]], [[6., 7.]]])

Notes ----- The function is applied to both the _data and the _mask, if any.

hstack( *args, **kwargs)

Stack arrays in sequence horizontally (column wise).

This is equivalent to concatenation along the second axis, except for 1-D arrays where it concatenates along the first axis. Rebuilds arrays divided by `hsplit`.

This function makes most sense for arrays with up to 3 dimensions. For instance, for pixel-data with a height (first axis), width (second axis), and r/g/b channels (third axis). The functions `concatenate`, `stack` and `block` provide more general stacking and concatenation operations.

Parameters ---------- tup : sequence of ndarrays The arrays must have the same shape along all but the second axis, except 1-D arrays which can be any length.

Returns ------- stacked : ndarray The array formed by stacking the given arrays.

See Also -------- stack : Join a sequence of arrays along a new axis. vstack : Stack arrays in sequence vertically (row wise). dstack : Stack arrays in sequence depth wise (along third axis). concatenate : Join a sequence of arrays along an existing axis. hsplit : Split array along second axis. block : Assemble arrays from blocks.

Examples -------- >>> a = np.array((1,2,3)) >>> b = np.array((2,3,4)) >>> np.hstack((a,b)) array(1, 2, 3, 2, 3, 4) >>> a = np.array([1],[2],[3]) >>> b = np.array([2],[3],[4]) >>> np.hstack((a,b)) array([1, 2], [2, 3], [3, 4])

Notes ----- The function is applied to both the _data and the _mask, if any.

Test whether each element of an array is also present in a second array.

The output is always a masked array. See `numpy.in1d` for more details.

We recommend using :func:`isin` instead of `in1d` for new code.

See Also -------- isin : Version of this function that preserves the shape of ar1. numpy.in1d : Equivalent function for ndarrays.

Notes ----- .. versionadded:: 1.4.0

Returns the unique elements common to both arrays.

Masked values are considered equal one to the other. The output is always a masked array.

See `numpy.intersect1d` for more details.

See Also -------- numpy.intersect1d : Equivalent function for ndarrays.

Examples -------- >>> x = np.ma.array(1, 3, 3, 3, mask=0, 0, 0, 1) >>> y = np.ma.array(3, 1, 1, 1, mask=0, 0, 0, 1) >>> np.ma.intersect1d(x, y) masked_array(data=1, 3, --, mask=False, False, True, fill_value=999999)

Calculates `element in test_elements`, broadcasting over `element` only.

The output is always a masked array of the same shape as `element`. See `numpy.isin` for more details.

See Also -------- in1d : Flattened version of this function. numpy.isin : Equivalent function for ndarrays.

Notes ----- .. versionadded:: 1.13.0

Is seq a sequence (ndarray, list or tuple)?

Construct a dtype description list from a given dtype.

Returns a new dtype object, with the type of all fields in `ndtype` to a boolean type. Field names are not altered.

Parameters ---------- ndtype : dtype The dtype to convert.

Returns ------- result : dtype A dtype that looks like `ndtype`, the type of all fields is boolean.

Examples -------- >>> import numpy.ma as ma >>> dtype = np.dtype('names':['foo', 'bar'], ... 'formats':[np.float32, np.int64]) >>> dtype dtype(('foo', '<f4'), ('bar', '<i8')) >>> ma.make_mask_descr(dtype) dtype(('foo', '|b1'), ('bar', '|b1')) >>> ma.make_mask_descr(np.float32) dtype('bool')

Mask columns of a 2D array that contain masked values.

This function is a shortcut to ``mask_rowcols`` with `axis` equal to 1.

See Also -------- mask_rowcols : Mask rows and/or columns of a 2D array. masked_where : Mask where a condition is met.

Examples -------- >>> import numpy.ma as ma >>> a = np.zeros((3, 3), dtype=int) >>> a1, 1 = 1 >>> a array([0, 0, 0], [0, 1, 0], [0, 0, 0]) >>> a = ma.masked_equal(a, 1) >>> a masked_array( data=[0, 0, 0], [0, --, 0], [0, 0, 0], mask=[False, False, False], [False, True, False], [False, False, False], fill_value=1) >>> ma.mask_cols(a) masked_array( data=[0, --, 0], [0, --, 0], [0, --, 0], mask=[False, True, False], [False, True, False], [False, True, False], fill_value=1)

Combine two masks with the ``logical_or`` operator.

The result may be a view on `m1` or `m2` if the other is `nomask` (i.e. False).

Parameters ---------- m1, m2 : array_like Input masks. copy : bool, optional If copy is False and one of the inputs is `nomask`, return a view of the other input mask. Defaults to False. shrink : bool, optional Whether to shrink the output to `nomask` if all its values are False. Defaults to True.

Returns ------- mask : output mask The result masks values that are masked in either `m1` or `m2`.

Raises ------ ValueError If `m1` and `m2` have different flexible dtypes.

Examples -------- >>> m1 = np.ma.make_mask(0, 1, 1, 0) >>> m2 = np.ma.make_mask(1, 0, 0, 0) >>> np.ma.mask_or(m1, m2) array( True, True, True, False)

Mask rows and/or columns of a 2D array that contain masked values.

Mask whole rows and/or columns of a 2D array that contain masked values. The masking behavior is selected using the `axis` parameter.

• If `axis` is None, rows *and* columns are masked.
• If `axis` is 0, only rows are masked.
• If `axis` is 1 or -1, only columns are masked.

Parameters ---------- a : array_like, MaskedArray The array to mask. If not a MaskedArray instance (or if no array elements are masked). The result is a MaskedArray with `mask` set to `nomask` (False). Must be a 2D array. axis : int, optional Axis along which to perform the operation. If None, applies to a flattened version of the array.

Returns ------- a : MaskedArray A modified version of the input array, masked depending on the value of the `axis` parameter.

Raises ------ NotImplementedError If input array `a` is not 2D.

See Also -------- mask_rows : Mask rows of a 2D array that contain masked values. mask_cols : Mask cols of a 2D array that contain masked values. masked_where : Mask where a condition is met.

Notes ----- The input array's mask is modified by this function.

Examples -------- >>> import numpy.ma as ma >>> a = np.zeros((3, 3), dtype=int) >>> a1, 1 = 1 >>> a array([0, 0, 0], [0, 1, 0], [0, 0, 0]) >>> a = ma.masked_equal(a, 1) >>> a masked_array( data=[0, 0, 0], [0, --, 0], [0, 0, 0], mask=[False, False, False], [False, True, False], [False, False, False], fill_value=1) >>> ma.mask_rowcols(a) masked_array( data=[0, --, 0], [--, --, --], [0, --, 0], mask=[False, True, False], [ True, True, True], [False, True, False], fill_value=1)

Mask rows of a 2D array that contain masked values.

This function is a shortcut to ``mask_rowcols`` with `axis` equal to 0.

See Also -------- mask_rowcols : Mask rows and/or columns of a 2D array. masked_where : Mask where a condition is met.

Examples -------- >>> import numpy.ma as ma >>> a = np.zeros((3, 3), dtype=int) >>> a1, 1 = 1 >>> a array([0, 0, 0], [0, 1, 0], [0, 0, 0]) >>> a = ma.masked_equal(a, 1) >>> a masked_array( data=[0, 0, 0], [0, --, 0], [0, 0, 0], mask=[False, False, False], [False, True, False], [False, False, False], fill_value=1)

>>> ma.mask_rows(a) masked_array( data=[0, 0, 0], [--, --, --], [0, 0, 0], mask=[False, False, False], [ True, True, True], [False, False, False], fill_value=1)

Empty masked array with all elements masked.

Return an empty masked array of the given shape and dtype, where all the data are masked.

Parameters ---------- shape : tuple Shape of the required MaskedArray. dtype : dtype, optional Data type of the output.

Returns ------- a : MaskedArray A masked array with all data masked.

See Also -------- masked_all_like : Empty masked array modelled on an existing array.

Examples -------- >>> import numpy.ma as ma >>> ma.masked_all((3, 3)) masked_array( data=[--, --, --], [--, --, --], [--, --, --], mask=[ True, True, True], [ True, True, True], [ True, True, True], fill_value=1e+20, dtype=float64)

The `dtype` parameter defines the underlying data type.

>>> a = ma.masked_all((3, 3)) >>> a.dtype dtype('float64') >>> a = ma.masked_all((3, 3), dtype=np.int32) >>> a.dtype dtype('int32')

Empty masked array with the properties of an existing array.

Return an empty masked array of the same shape and dtype as the array `arr`, where all the data are masked.

Parameters ---------- arr : ndarray An array describing the shape and dtype of the required MaskedArray.

Returns ------- a : MaskedArray A masked array with all data masked.

Raises ------ AttributeError If `arr` doesn't have a shape attribute (i.e. not an ndarray)

See Also -------- masked_all : Empty masked array with all elements masked.

Examples -------- >>> import numpy.ma as ma >>> arr = np.zeros((2, 3), dtype=np.float32) >>> arr array([0., 0., 0.], [0., 0., 0.], dtype=float32) >>> ma.masked_all_like(arr) masked_array( data=[--, --, --], [--, --, --], mask=[ True, True, True], [ True, True, True], fill_value=1e+20, dtype=float32)

The dtype of the masked array matches the dtype of `arr`.

>>> arr.dtype dtype('float32') >>> ma.masked_all_like(arr).dtype dtype('float32')

Compute the median along the specified axis.

Returns the median of the array elements.

Parameters ---------- a : array_like Input array or object that can be converted to an array. axis : int, optional Axis along which the medians are computed. The default (None) is to compute the median along a flattened version of the array. out : ndarray, optional Alternative output array in which to place the result. It must have the same shape and buffer length as the expected output but the type will be cast if necessary. overwrite_input : bool, optional If True, then allow use of memory of input array (a) for calculations. The input array will be modified by the call to median. This will save memory when you do not need to preserve the contents of the input array. Treat the input as undefined, but it will probably be fully or partially sorted. Default is False. Note that, if `overwrite_input` is True, and the input is not already an `ndarray`, an error will be raised. 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.

.. versionadded:: 1.10.0

Returns ------- median : ndarray A new array holding the result is returned unless out is specified, in which case a reference to out is returned. Return data-type is `float64` for integers and floats smaller than `float64`, or the input data-type, otherwise.

See Also -------- mean

Notes ----- Given a vector ``V`` with ``N`` non masked values, the median of ``V`` is the middle value of a sorted copy of ``V`` (``Vs``) - i.e. ``Vs(N-1)/2``, when ``N`` is odd, or ``Vs[N/2 - 1] + Vs[N/2]/2`` when ``N`` is even.

Examples -------- >>> x = np.ma.array(np.arange(8), mask=0*4 + 1*4) >>> np.ma.median(x) 1.5

>>> x = np.ma.array(np.arange(10).reshape(2, 5), mask=0*6 + 1*4) >>> np.ma.median(x) 2.5 >>> np.ma.median(x, axis=-1, overwrite_input=True) masked_array(data=2.0, 5.0, mask=False, False, fill_value=1e+20)

normalize_axis_index(axis, ndim, msg_prefix=None)

Normalizes an axis index, `axis`, such that is a valid positive index into the shape of array with `ndim` dimensions. Raises an AxisError with an appropriate message if this is not possible.

Used internally by all axis-checking logic.

.. versionadded:: 1.13.0

Parameters ---------- axis : int The un-normalized index of the axis. Can be negative ndim : int The number of dimensions of the array that `axis` should be normalized against msg_prefix : str A prefix to put before the message, typically the name of the argument

Returns ------- normalized_axis : int The normalized axis index, such that `0 <= normalized_axis < ndim`

Raises ------ AxisError If the axis index is invalid, when `-ndim <= axis < ndim` is false.

Examples -------- >>> normalize_axis_index(0, ndim=3) 0 >>> normalize_axis_index(1, ndim=3) 1 >>> normalize_axis_index(-1, ndim=3) 2

>>> normalize_axis_index(3, ndim=3) Traceback (most recent call last): ... AxisError: axis 3 is out of bounds for array of dimension 3 >>> normalize_axis_index(-4, ndim=3, msg_prefix='axes_arg') Traceback (most recent call last): ... AxisError: axes_arg: axis -4 is out of bounds for array of dimension 3

Normalizes an axis argument into a tuple of non-negative integer axes.

This handles shorthands such as ``1`` and converts them to ``(1,)``, as well as performing the handling of negative indices covered by `normalize_axis_index`.

By default, this forbids axes from being specified multiple times.

Used internally by multi-axis-checking logic.

.. versionadded:: 1.13.0

Parameters ---------- axis : int, iterable of int The un-normalized index or indices of the axis. ndim : int The number of dimensions of the array that `axis` should be normalized against. argname : str, optional A prefix to put before the error message, typically the name of the argument. allow_duplicate : bool, optional If False, the default, disallow an axis from being specified twice.

Returns ------- normalized_axes : tuple of int The normalized axis index, such that `0 <= normalized_axis < ndim`

Raises ------ AxisError If any axis provided is out of range ValueError If an axis is repeated

See also -------- normalize_axis_index : normalizing a single scalar axis

Find contiguous unmasked data in a masked array along the given axis.

Parameters ---------- a : array_like The input array. axis : int, optional Axis along which to perform the operation. If None (default), applies to a flattened version of the array, and this is the same as `flatnotmasked_contiguous`.

Returns ------- endpoints : list A list of slices (start and end indexes) of unmasked indexes in the array.

If the input is 2d and axis is specified, the result is a list of lists.

See Also -------- flatnotmasked_edges, flatnotmasked_contiguous, notmasked_edges clump_masked, clump_unmasked

Notes ----- Only accepts 2-D arrays at most.

Examples -------- >>> a = np.arange(12).reshape((3, 4)) >>> mask = np.zeros_like(a) >>> mask1:, :-1 = 1; mask0, 1 = 1; mask-1, 0 = 0 >>> ma = np.ma.array(a, mask=mask) >>> ma masked_array( data=[0, --, 2, 3], [--, --, --, 7], [8, --, --, 11], mask=[False, True, False, False], [ True, True, True, False], [False, True, True, False], fill_value=999999) >>> np.array(ma~ma.mask) array( 0, 2, 3, 7, 8, 11)

>>> np.ma.notmasked_contiguous(ma) slice(0, 1, None), slice(2, 4, None), slice(7, 9, None), slice(11, 12, None)

>>> np.ma.notmasked_contiguous(ma, axis=0) [slice(0, 1, None), slice(2, 3, None)], [], [slice(0, 1, None)], [slice(0, 3, None)]

>>> np.ma.notmasked_contiguous(ma, axis=1) [slice(0, 1, None), slice(2, 4, None)], [slice(3, 4, None)], [slice(0, 1, None), slice(3, 4, None)]

Find the indices of the first and last unmasked values along an axis.

If all values are masked, return None. Otherwise, return a list of two tuples, corresponding to the indices of the first and last unmasked values respectively.

Parameters ---------- a : array_like The input array. axis : int, optional Axis along which to perform the operation. If None (default), applies to a flattened version of the array.

Returns ------- edges : ndarray or list An array of start and end indexes if there are any masked data in the array. If there are no masked data in the array, `edges` is a list of the first and last index.

See Also -------- flatnotmasked_contiguous, flatnotmasked_edges, notmasked_contiguous clump_masked, clump_unmasked

Examples -------- >>> a = np.arange(9).reshape((3, 3)) >>> m = np.zeros_like(a) >>> m1:, 1: = 1

>>> am = np.ma.array(a, mask=m) >>> np.array(am~am.mask) array(0, 1, 2, 3, 6)

>>> np.ma.notmasked_edges(am) array(0, 6)

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])

ones(shape, dtype=None, order='C')

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

Parameters ---------- shape : int or sequence 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 ones with the given shape, dtype, and order.

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

Examples -------- >>> np.ones(5) array(1., 1., 1., 1., 1.)

>>> np.ones((5,), dtype=int) array(1, 1, 1, 1, 1)

>>> np.ones((2, 1)) array([1.], [1.])

>>> s = (2,2) >>> np.ones(s) array([1., 1.], [1., 1.])

Least squares polynomial fit.

Fit a polynomial ``p(x) = p0 * x**deg + ... + pdeg`` of degree `deg` to points `(x, y)`. Returns a vector of coefficients `p` that minimises the squared error in the order `deg`, `deg-1`, ... `0`.

The `Polynomial.fit <numpy.polynomial.polynomial.Polynomial.fit>` class method is recommended for new code as it is more stable numerically. See the documentation of the method for more information.

Parameters ---------- x : array_like, shape (M,) x-coordinates of the M sample points ``(xi, yi)``. y : array_like, shape (M,) or (M, K) y-coordinates of the sample points. Several data sets of sample points sharing the same x-coordinates can be fitted at once by passing in a 2D-array that contains one dataset per column. deg : int Degree of the fitting polynomial rcond : float, optional Relative condition number of the fit. Singular values smaller than this relative to the largest singular value will be ignored. The default value is len(x)*eps, where eps is the relative precision of the float type, about 2e-16 in most cases. full : bool, optional Switch determining nature of return value. When it is False (the default) just the coefficients are returned, when True diagnostic information from the singular value decomposition is also returned. w : array_like, shape (M,), optional Weights to apply to the y-coordinates of the sample points. For gaussian uncertainties, use 1/sigma (not 1/sigma**2). cov : bool or str, optional If given and not `False`, return not just the estimate but also its covariance matrix. By default, the covariance are scaled by chi2/sqrt(N-dof), i.e., the weights are presumed to be unreliable except in a relative sense and everything is scaled such that the reduced chi2 is unity. This scaling is omitted if ``cov='unscaled'``, as is relevant for the case that the weights are 1/sigma**2, with sigma known to be a reliable estimate of the uncertainty.

Returns ------- p : ndarray, shape (deg + 1,) or (deg + 1, K) Polynomial coefficients, highest power first. If `y` was 2-D, the coefficients for `k`-th data set are in ``p:,k``.

residuals, rank, singular_values, rcond Present only if `full` = True. Residuals is sum of squared residuals of the least-squares fit, the effective rank of the scaled Vandermonde coefficient matrix, its singular values, and the specified value of `rcond`. For more details, see `linalg.lstsq`.

V : ndarray, shape (M,M) or (M,M,K) Present only if `full` = False and `cov`=True. The covariance matrix of the polynomial coefficient estimates. The diagonal of this matrix are the variance estimates for each coefficient. If y is a 2-D array, then the covariance matrix for the `k`-th data set are in ``V:,:,k``

Warns ----- RankWarning The rank of the coefficient matrix in the least-squares fit is deficient. The warning is only raised if `full` = False.

The warnings can be turned off by

>>> import warnings >>> warnings.simplefilter('ignore', np.RankWarning)

See Also -------- polyval : Compute polynomial values. linalg.lstsq : Computes a least-squares fit. scipy.interpolate.UnivariateSpline : Computes spline fits.

Notes -----

Any masked values in x is propagated in y, and vice-versa.

The solution minimizes the squared error

.. math :: E = \sum_j=0^k |p(x_j) - y_j|^2

in the equations::

x0**n * p0 + ... + x0 * pn-1 + pn = y0 x1**n * p0 + ... + x1 * pn-1 + pn = y1 ... xk**n * p0 + ... + xk * pn-1 + pn = yk

The coefficient matrix of the coefficients `p` is a Vandermonde matrix.

`polyfit` issues a `RankWarning` when the least-squares fit is badly conditioned. This implies that the best fit is not well-defined due to numerical error. The results may be improved by lowering the polynomial degree or by replacing `x` by `x` - `x`.mean(). The `rcond` parameter can also be set to a value smaller than its default, but the resulting fit may be spurious: including contributions from the small singular values can add numerical noise to the result.

Note that fitting polynomial coefficients is inherently badly conditioned when the degree of the polynomial is large or the interval of sample points is badly centered. The quality of the fit should always be checked in these cases. When polynomial fits are not satisfactory, splines may be a good alternative.

References ---------- .. 1 Wikipedia, 'Curve fitting', https://en.wikipedia.org/wiki/Curve_fitting .. 2 Wikipedia, 'Polynomial interpolation', https://en.wikipedia.org/wiki/Polynomial_interpolation

Examples -------- >>> import warnings >>> x = np.array(0.0, 1.0, 2.0, 3.0, 4.0, 5.0) >>> y = np.array(0.0, 0.8, 0.9, 0.1, -0.8, -1.0) >>> z = np.polyfit(x, y, 3) >>> z array( 0.08703704, -0.81349206, 1.69312169, -0.03968254) # may vary

It is convenient to use `poly1d` objects for dealing with polynomials:

>>> p = np.poly1d(z) >>> p(0.5) 0.6143849206349179 # may vary >>> p(3.5) -0.34732142857143039 # may vary >>> p(10) 22.579365079365115 # may vary

High-order polynomials may oscillate wildly:

>>> with warnings.catch_warnings(): ... warnings.simplefilter('ignore', np.RankWarning) ... p30 = np.poly1d(np.polyfit(x, y, 30)) ... >>> p30(4) -0.80000000000000204 # may vary >>> p30(5) -0.99999999999999445 # may vary >>> p30(4.5) -0.10547061179440398 # may vary

Illustration:

>>> import matplotlib.pyplot as plt >>> xp = np.linspace(-2, 6, 100) >>> _ = plt.plot(x, y, '.', xp, p(xp), '-', xp, p30(xp), '--') >>> plt.ylim(-2,2) (-2, 2) >>> plt.show()

vstack( *args, **kwargs)

Stack arrays in sequence vertically (row wise).

This is equivalent to concatenation along the first axis after 1-D arrays of shape `(N,)` have been reshaped to `(1,N)`. Rebuilds arrays divided by `vsplit`.

This function makes most sense for arrays with up to 3 dimensions. For instance, for pixel-data with a height (first axis), width (second axis), and r/g/b channels (third axis). The functions `concatenate`, `stack` and `block` provide more general stacking and concatenation operations.

Parameters ---------- tup : sequence of ndarrays The arrays must have the same shape along all but the first axis. 1-D arrays must have the same length.

Returns ------- stacked : ndarray The array formed by stacking the given arrays, will be at least 2-D.

See Also -------- stack : Join a sequence of arrays along a new axis. hstack : Stack arrays in sequence horizontally (column wise). dstack : Stack arrays in sequence depth wise (along third dimension). concatenate : Join a sequence of arrays along an existing axis. vsplit : Split array into a list of multiple sub-arrays vertically. block : Assemble arrays from blocks.

Examples -------- >>> a = np.array(1, 2, 3) >>> b = np.array(2, 3, 4) >>> np.vstack((a,b)) array([1, 2, 3], [2, 3, 4])

>>> a = np.array([1], [2], [3]) >>> b = np.array([2], [3], [4]) >>> np.vstack((a,b)) array([1], [2], [3], [2], [3], [4])

Notes ----- The function is applied to both the _data and the _mask, if any.

Set difference of 1D arrays with unique elements.

The output is always a masked array. See `numpy.setdiff1d` for more details.

See Also -------- numpy.setdiff1d : Equivalent function for ndarrays.

Examples -------- >>> x = np.ma.array(1, 2, 3, 4, mask=0, 1, 0, 1) >>> np.ma.setdiff1d(x, 1, 2) masked_array(data=3, --, mask=False, True, fill_value=999999)

Set exclusive-or of 1-D arrays with unique elements.

The output is always a masked array. See `numpy.setxor1d` for more details.

See Also -------- numpy.setxor1d : Equivalent function for ndarrays.

Sort the array, in-place

Parameters ---------- a : array_like Array to be sorted. axis : int, 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 The sorting algorithm used. order : list, optional When `a` is a structured array, this argument specifies which fields to compare first, second, and so on. This list does not need to include all of the fields. endwith : True, False, optional Whether missing values (if any) should be treated as the largest values (True) or the smallest values (False) When the array contains unmasked values sorting at the same extremes of the datatype, the ordering of these values and the masked values is undefined. fill_value :

ar}, optional
    Value used internally for the masked values.
    If ``fill_value`` is not None, it supersedes ``endwith``.

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

See Also
--------
numpy.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.

Notes
-----
See ``sort`` for notes on the different sorting algorithms.

Examples
--------
>>> a = np.ma.array([1, 2, 5, 4, 3],mask=[0, 1, 0, 1, 0])
>>> # Default
>>> a.sort()
>>> a
masked_array(data=[1, 3, 5, --, --],
             mask=[False, False, False,  True,  True],
       fill_value=999999)

>>> a = np.ma.array([1, 2, 5, 4, 3],mask=[0, 1, 0, 1, 0])
>>> # Put missing values in the front
>>> a.sort(endwith=False)
>>> a
masked_array(data=[--, --, 1, 3, 5],
             mask=[ True,  True, False, False, False],
       fill_value=999999)

>>> a = np.ma.array([1, 2, 5, 4, 3],mask=[0, 1, 0, 1, 0])
>>> # fill_value takes over endwith
>>> a.sort(endwith=False, fill_value=3)
>>> a
masked_array(data=[1, --, --, 3, 5],
             mask=[False,  True,  True, False, False],
       fill_value=999999)

stack( *args, **kwargs)

Join a sequence of arrays along a new axis.

The ``axis`` parameter specifies the index of the new axis in the dimensions of the result. For example, if ``axis=0`` it will be the first dimension and if ``axis=-1`` it will be the last dimension.

.. versionadded:: 1.10.0

Parameters ---------- arrays : sequence of array_like Each array must have the same shape.

axis : int, optional The axis in the result array along which the input arrays are stacked.

out : ndarray, optional If provided, the destination to place the result. The shape must be correct, matching that of what stack would have returned if no out argument were specified.

Returns ------- stacked : ndarray The stacked array has one more dimension than the input arrays.

See Also -------- concatenate : Join a sequence of arrays along an existing axis. split : Split array into a list of multiple sub-arrays of equal size. block : Assemble arrays from blocks.

Examples -------- >>> arrays = np.random.randn(3, 4) for _ in range(10) >>> np.stack(arrays, axis=0).shape (10, 3, 4)

>>> np.stack(arrays, axis=1).shape (3, 10, 4)

>>> np.stack(arrays, axis=2).shape (3, 4, 10)

>>> a = np.array(1, 2, 3) >>> b = np.array(2, 3, 4) >>> np.stack((a, b)) array([1, 2, 3], [2, 3, 4])

>>> np.stack((a, b), axis=-1) array([1, 2], [2, 3], [3, 4])

Notes ----- The function is applied to both the _data and the _mask, if any.

Union of two arrays.

The output is always a masked array. See `numpy.union1d` for more details.

See also -------- numpy.union1d : Equivalent function for ndarrays.

Finds the unique elements of an array.

Masked values are considered the same element (masked). The output array is always a masked array. See `numpy.unique` for more details.

See Also -------- numpy.unique : Equivalent function for ndarrays.

Generate a Vandermonde matrix.

The columns of the output matrix are powers of the input vector. The order of the powers is determined by the `increasing` boolean argument. Specifically, when `increasing` is False, the `i`-th output column is the input vector raised element-wise to the power of ``N - i - 1``. Such a matrix with a geometric progression in each row is named for Alexandre- Theophile Vandermonde.

Parameters ---------- x : array_like 1-D input array. N : int, optional Number of columns in the output. If `N` is not specified, a square array is returned (``N = len(x)``). increasing : bool, optional Order of the powers of the columns. If True, the powers increase from left to right, if False (the default) they are reversed.

.. versionadded:: 1.9.0

Returns ------- out : ndarray Vandermonde matrix. If `increasing` is False, the first column is ``x^(N-1)``, the second ``x^(N-2)`` and so forth. If `increasing` is True, the columns are ``x^0, x^1, ..., x^(N-1)``.

See Also -------- polynomial.polynomial.polyvander

Examples -------- >>> x = np.array(1, 2, 3, 5) >>> N = 3 >>> np.vander(x, N) array([ 1, 1, 1], [ 4, 2, 1], [ 9, 3, 1], [25, 5, 1])

>>> np.column_stack(x**(N-1-i) for i in range(N)) array([ 1, 1, 1], [ 4, 2, 1], [ 9, 3, 1], [25, 5, 1])

>>> x = np.array(1, 2, 3, 5) >>> np.vander(x) array([ 1, 1, 1, 1], [ 8, 4, 2, 1], [ 27, 9, 3, 1], [125, 25, 5, 1]) >>> np.vander(x, increasing=True) array([ 1, 1, 1, 1], [ 1, 2, 4, 8], [ 1, 3, 9, 27], [ 1, 5, 25, 125])

The determinant of a square Vandermonde matrix is the product of the differences between the values of the input vector:

>>> np.linalg.det(np.vander(x)) 48.000000000000043 # may vary >>> (5-3)*(5-2)*(5-1)*(3-2)*(3-1)*(2-1) 48

Notes -----

Masked values in the input array result in rows of zeros.

vstack( *args, **kwargs)

Stack arrays in sequence vertically (row wise).

This is equivalent to concatenation along the first axis after 1-D arrays of shape `(N,)` have been reshaped to `(1,N)`. Rebuilds arrays divided by `vsplit`.

This function makes most sense for arrays with up to 3 dimensions. For instance, for pixel-data with a height (first axis), width (second axis), and r/g/b channels (third axis). The functions `concatenate`, `stack` and `block` provide more general stacking and concatenation operations.

Parameters ---------- tup : sequence of ndarrays The arrays must have the same shape along all but the first axis. 1-D arrays must have the same length.

Returns ------- stacked : ndarray The array formed by stacking the given arrays, will be at least 2-D.

See Also -------- stack : Join a sequence of arrays along a new axis. hstack : Stack arrays in sequence horizontally (column wise). dstack : Stack arrays in sequence depth wise (along third dimension). concatenate : Join a sequence of arrays along an existing axis. vsplit : Split array into a list of multiple sub-arrays vertically. block : Assemble arrays from blocks.

Examples -------- >>> a = np.array(1, 2, 3) >>> b = np.array(2, 3, 4) >>> np.vstack((a,b)) array([1, 2, 3], [2, 3, 4])

>>> a = np.array([1], [2], [3]) >>> b = np.array([2], [3], [4]) >>> np.vstack((a,b)) array([1], [2], [3], [2], [3], [4])

Notes ----- The function is applied to both the _data and the _mask, if any.

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'))