test_multiclass.py 文件源码

def test_ovr_single_label_predict_proba():
    base_clf = MultinomialNB(alpha=1)
    X, Y = iris.data, iris.target
    X_train, Y_train = X[:80], Y[:80]
    X_test = X[80:]
    clf = OneVsRestClassifier(base_clf).fit(X_train, Y_train)

    # decision function only estimator. Fails in current implementation.
    decision_only = OneVsRestClassifier(svm.SVR()).fit(X_train, Y_train)
    assert_raises(AttributeError, decision_only.predict_proba, X_test)

    Y_pred = clf.predict(X_test)
    Y_proba = clf.predict_proba(X_test)

    assert_almost_equal(Y_proba.sum(axis=1), 1.0)
    # predict assigns a label if the probability that the
    # sample has the label is greater than 0.5.
    pred = np.array([l.argmax() for l in Y_proba])
    assert_false((pred - Y_pred).any())