sklearn.metrics.pairwise.polynomial_kernel(X, Y=None, degree=3, gamma=None, coef0=1)[source]

Compute the polynomial kernel between X and Y.

\(K(X, Y) = (gamma <X, Y> + coef0)^{degree}\)

Read more in the User Guide.

Xndarray of shape (n_samples_X, n_features)

A feature array.

Yndarray of shape (n_samples_Y, n_features), default=None

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

degreeint, default=3

Kernel degree.

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.

Gram matrixndarray of shape (n_samples_X, n_samples_Y)

The polynomial kernel.