Note

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This example illustrates the differences between univariate F-test statistics and mutual information.

We consider 3 features x_1, x_2, x_3 distributed uniformly over [0, 1], the target depends on them as follows:

y = x_1 + sin(6 * pi * x_2) + 0.1 * N(0, 1), that is the third features is completely irrelevant.

The code below plots the dependency of y against individual x_i and normalized values of univariate F-tests statistics and mutual information.

As F-test captures only linear dependency, it rates x_1 as the most discriminative feature. On the other hand, mutual information can capture any kind of dependency between variables and it rates x_2 as the most discriminative feature, which probably agrees better with our intuitive perception for this example. Both methods correctly marks x_3 as irrelevant.

print(__doc__) import numpy as np import matplotlib.pyplot as plt from sklearn.feature_selection import f_regression, mutual_info_regression np.random.seed(0) X = np.random.rand(1000, 3) y = X[:, 0] + np.sin(6 * np.pi * X[:, 1]) + 0.1 * np.random.randn(1000) f_test, _ = f_regression(X, y) f_test /= np.max(f_test) mi = mutual_info_regression(X, y) mi /= np.max(mi) plt.figure(figsize=(15, 5)) for i in range(3): plt.subplot(1, 3, i + 1) plt.scatter(X[:, i], y, edgecolor='black', s=20) plt.xlabel("$x_{}$".format(i + 1), fontsize=14) if i == 0: plt.ylabel("$y$", fontsize=14) plt.title("F-test={:.2f}, MI={:.2f}".format(f_test[i], mi[i]), fontsize=16) plt.show()

**Total running time of the script:** ( 0 minutes 0.101 seconds)

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http://scikit-learn.org/stable/auto_examples/feature_selection/plot_f_test_vs_mi.html