sklearn.metrics.pairwise.sigmoid_kernel

sklearn.metrics.pairwise.sigmoid_kernel(X, Y=None, gamma=None, coef0=1)

Compute the sigmoid kernel between X and Y.

K(X, Y) = tanh(gamma <X, Y> + coef0)

Read more in the User Guide.

Parameters:

X{array-like, sparse matrix} of shape (n_samples_X, n_features)

A feature array.

Y{array-like, sparse matrix} of shape (n_samples_Y, n_features), default=None

An optional second feature array. If None, uses Y=X.

gammafloat, default=None

Coefficient of the vector inner product. If None, defaults to 1.0 / n_features.

coef0float, default=1

Constant offset added to scaled inner product.

Returns:

kernelndarray of shape (n_samples_X, n_samples_Y)

Sigmoid kernel between two arrays.

Examples

>>> from sklearn.metrics.pairwise import sigmoid_kernel
>>> X = [[0, 0, 0], [1, 1, 1]]
>>> Y = [[1, 0, 0], [1, 1, 0]]
>>> sigmoid_kernel(X, Y)
array([[0.76..., 0.76...],
       [0.87..., 0.93...]])