`sklearn.gaussian_process.kernels`.Sum¶

class sklearn.gaussian_process.kernels.Sum(k1, k2)[source]¶

The Sum kernel takes two kernels \(k_1\) and \(k_2\) and combines them via

\[k_{sum}(X, Y) = k_1(X, Y) + k_2(X, Y)\]

Note that the __add__ magic method is overridden, so Sum(RBF(), RBF()) is equivalent to using the + operator with RBF() + RBF().

Read more in the User Guide.

New in version 0.18.

Parameters

k1Kernel: The first base-kernel of the sum-kernel
k2Kernel: The second base-kernel of the sum-kernel

Attributes

bounds: Returns the log-transformed bounds on the theta.
hyperparameters: Returns a list of all hyperparameter.
n_dims: Returns the number of non-fixed hyperparameters of the kernel.
requires_vector_input: Returns whether the kernel is stationary.
theta: Returns the (flattened, log-transformed) non-fixed hyperparameters.

Examples

>>> from sklearn.datasets import make_friedman2
>>> from sklearn.gaussian_process import GaussianProcessRegressor
>>> from sklearn.gaussian_process.kernels import RBF, Sum, ConstantKernel
>>> X, y = make_friedman2(n_samples=500, noise=0, random_state=0)
>>> kernel = Sum(ConstantKernel(2), RBF())
>>> gpr = GaussianProcessRegressor(kernel=kernel,
...         random_state=0).fit(X, y)
>>> gpr.score(X, y)
1.0
>>> kernel
1.41**2 + RBF(length_scale=1)

Methods

`__call__`(X[, Y, eval_gradient])	Return the kernel k(X, Y) and optionally its gradient.
`clone_with_theta`(theta)	Returns a clone of self with given hyperparameters theta.
`diag`(X)	Returns the diagonal of the kernel k(X, X).
`get_params`([deep])	Get parameters of this kernel.
`is_stationary`()	Returns whether the kernel is stationary.
`set_params`(**params)	Set the parameters of this kernel.

__call__(X, Y=None, eval_gradient=False)[source]¶

Return the kernel k(X, Y) and optionally its gradient.

Parameters

Xarray-like of shape (n_samples_X, n_features) or list of object: Left argument of the returned kernel k(X, Y)
Yarray-like of shape (n_samples_X, n_features) or list of object, default=None: Right argument of the returned kernel k(X, Y). If None, k(X, X) is evaluated instead.
eval_gradientbool, default=False: Determines whether the gradient with respect to the log of the kernel hyperparameter is computed.

Returns

Kndarray of shape (n_samples_X, n_samples_Y): Kernel k(X, Y)
K_gradientndarray of shape (n_samples_X, n_samples_X, n_dims), optional: The gradient of the kernel k(X, X) with respect to the log of the hyperparameter of the kernel. Only returned when eval_gradient is True.

property bounds¶

Returns the log-transformed bounds on the theta.

Returns

boundsndarray of shape (n_dims, 2): The log-transformed bounds on the kernel’s hyperparameters theta

clone_with_theta(theta)[source]¶

Returns a clone of self with given hyperparameters theta.

Parameters

thetandarray of shape (n_dims,): The hyperparameters

diag(X)[source]¶

Returns the diagonal of the kernel k(X, X).

The result of this method is identical to np.diag(self(X)); however, it can be evaluated more efficiently since only the diagonal is evaluated.

Parameters

Xarray-like of shape (n_samples_X, n_features) or list of object: Argument to the kernel.

Returns

K_diagndarray of shape (n_samples_X,): Diagonal of kernel k(X, X)

get_params(deep=True)[source]¶

Get parameters of this kernel.

Parameters

deepbool, default=True: If True, will return the parameters for this estimator and contained subobjects that are estimators.

Returns

paramsdict: Parameter names mapped to their values.

property hyperparameters¶: Returns a list of all hyperparameter.

is_stationary()[source]¶: Returns whether the kernel is stationary.

property n_dims¶: Returns the number of non-fixed hyperparameters of the kernel.

property requires_vector_input¶: Returns whether the kernel is stationary.

set_params(**params)[source]¶

Set the parameters of this kernel.

The method works on simple kernels as well as on nested kernels. The latter have parameters of the form <component>__<parameter> so that it’s possible to update each component of a nested object.

Returns

self

property theta¶

Returns the (flattened, log-transformed) non-fixed hyperparameters.

Note that theta are typically the log-transformed values of the kernel’s hyperparameters as this representation of the search space is more amenable for hyperparameter search, as hyperparameters like length-scales naturally live on a log-scale.

Returns

thetandarray of shape (n_dims,): The non-fixed, log-transformed hyperparameters of the kernel

sklearn.gaussian_process.kernels.Sum¶

`sklearn.gaussian_process.kernels`.Sum¶