test_svm.py 文件源码

def test_decision_function():
    # Test decision_function
    # Sanity check, test that decision_function implemented in python
    # returns the same as the one in libsvm
    # multi class:
    clf = svm.SVC(kernel='linear', C=0.1,
                  decision_function_shape='ovo').fit(iris.data, iris.target)

    dec = np.dot(iris.data, clf.coef_.T) + clf.intercept_

    assert_array_almost_equal(dec, clf.decision_function(iris.data))

    # binary:
    clf.fit(X, Y)
    dec = np.dot(X, clf.coef_.T) + clf.intercept_
    prediction = clf.predict(X)
    assert_array_almost_equal(dec.ravel(), clf.decision_function(X))
    assert_array_almost_equal(
        prediction,
        clf.classes_[(clf.decision_function(X) > 0).astype(np.int)])
    expected = np.array([-1., -0.66, -1., 0.66, 1., 1.])
    assert_array_almost_equal(clf.decision_function(X), expected, 2)

    # kernel binary:
    clf = svm.SVC(kernel='rbf', gamma=1, decision_function_shape='ovo')
    clf.fit(X, Y)

    rbfs = rbf_kernel(X, clf.support_vectors_, gamma=clf.gamma)
    dec = np.dot(rbfs, clf.dual_coef_.T) + clf.intercept_
    assert_array_almost_equal(dec.ravel(), clf.decision_function(X))