test_sgd.py 文件源码

def test_l1_ratio():
    # Test if l1 ratio extremes match L1 and L2 penalty settings.
    X, y = datasets.make_classification(n_samples=1000,
                                        n_features=100, n_informative=20,
                                        random_state=1234)

    # test if elasticnet with l1_ratio near 1 gives same result as pure l1
    est_en = SGDClassifier(alpha=0.001, penalty='elasticnet',
                           l1_ratio=0.9999999999, random_state=42).fit(X, y)
    est_l1 = SGDClassifier(alpha=0.001, penalty='l1', random_state=42).fit(X, y)
    assert_array_almost_equal(est_en.coef_, est_l1.coef_)

    # test if elasticnet with l1_ratio near 0 gives same result as pure l2
    est_en = SGDClassifier(alpha=0.001, penalty='elasticnet',
                           l1_ratio=0.0000000001, random_state=42).fit(X, y)
    est_l2 = SGDClassifier(alpha=0.001, penalty='l2', random_state=42).fit(X, y)
    assert_array_almost_equal(est_en.coef_, est_l2.coef_)