Wrapper for kernels in sklearn.metrics.pairwise.
A thin wrapper around the functionality of the kernels in sklearn.metrics.pairwise.
Note: Evaluation of eval_gradient is not analytic but numeric and all kernels support only isotropic distances. The parameter gamma is considered to be a hyperparameter and may be optimized. The other kernel parameters are set directly at initialization and are kept fixed.
.. versionadded:: 0.18
Parameters ---------- gamma : float, default=1.0 Parameter gamma of the pairwise kernel specified by metric. It should be positive.
gamma_bounds : pair of floats >= 0 or 'fixed', default=(1e-5, 1e5) The lower and upper bound on 'gamma'. If set to 'fixed', 'gamma' cannot be changed during hyperparameter tuning.
metric : 'linear', 'additive_chi2', 'chi2', 'poly', 'polynomial', 'rbf', 'laplacian', 'sigmoid', 'cosine' or callable, default='linear' The metric to use when calculating kernel between instances in a feature array. If metric is a string, it must be one of the metrics in pairwise.PAIRWISE_KERNEL_FUNCTIONS. If metric is 'precomputed', X is assumed to be a kernel matrix. Alternatively, if metric is a callable function, it is called on each pair of instances (rows) and the resulting value recorded. The callable should take two arrays from X as input and return a value indicating the distance between them.
pairwise_kernels_kwargs : dict, default=None All entries of this dict (if any) are passed as keyword arguments to the pairwise kernel function.