Kernel ridge

This example demonstrates how to solve kernel ridge regression, using himalaya’s estimator KernelRidge compatible with scikit-learn’s API.

Create a random dataset

import numpy as np
n_samples, n_features, n_targets = 10, 20, 4
X = np.random.randn(n_samples, n_features)
Y = np.random.randn(n_samples, n_targets)

Scikit-learn API

Himalaya implements a KernelRidge estimator, similar to the corresponding scikit-learn estimator, with similar parameters and methods.

import sklearn.kernel_ridge
import himalaya.kernel_ridge

# Fit a scikit-learn model
model_skl = sklearn.kernel_ridge.KernelRidge(kernel="linear", alpha=0.1)
model_skl.fit(X, Y)

# Fit a himalaya model
model_him = himalaya.kernel_ridge.KernelRidge(kernel="linear", alpha=0.1)
model_him.fit(X, Y)

Y_pred_skl = model_skl.predict(X)
Y_pred_him = model_him.predict(X)

# The predictions are virtually identical.
print(np.max(np.abs(Y_pred_skl - Y_pred_him)))

2.5979218776228663e-14

Small API difference

Since himalaya focuses on fitting multiple targets, the score method returns the score on each target separately, while scikit-learn returns the average score over targets.

print(model_skl.score(X, Y))
print(model_him.score(X, Y))
print(model_him.score(X, Y).mean())

0.9976892308577026
[0.99878788 0.99718964 0.9972637  0.99751571]
0.9976892308577028