561 lines
21 KiB
Python
561 lines
21 KiB
Python
# Authors: Alexandre Gramfort <alexandre.gramfort@telecom-paristech.fr>
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# License: BSD 3 clause
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import pytest
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import numpy as np
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from numpy.testing import assert_allclose
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from scipy import sparse
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from sklearn.base import BaseEstimator
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from sklearn.model_selection import LeaveOneOut, train_test_split
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from sklearn.utils._testing import (assert_array_almost_equal,
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assert_almost_equal,
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assert_array_equal,
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assert_raises, ignore_warnings)
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from sklearn.utils.extmath import softmax
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from sklearn.exceptions import NotFittedError
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from sklearn.datasets import make_classification, make_blobs
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from sklearn.preprocessing import LabelEncoder
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from sklearn.model_selection import KFold, cross_val_predict
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from sklearn.naive_bayes import MultinomialNB
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from sklearn.ensemble import RandomForestClassifier, RandomForestRegressor
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from sklearn.svm import LinearSVC
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from sklearn.isotonic import IsotonicRegression
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from sklearn.feature_extraction import DictVectorizer
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from sklearn.pipeline import Pipeline
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from sklearn.impute import SimpleImputer
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from sklearn.metrics import brier_score_loss
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from sklearn.calibration import CalibratedClassifierCV
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from sklearn.calibration import _sigmoid_calibration, _SigmoidCalibration
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from sklearn.calibration import calibration_curve
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@pytest.fixture(scope="module")
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def data():
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X, y = make_classification(
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n_samples=200, n_features=6, random_state=42
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)
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return X, y
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@pytest.mark.parametrize('method', ['sigmoid', 'isotonic'])
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@pytest.mark.parametrize('ensemble', [True, False])
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def test_calibration(data, method, ensemble):
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# Test calibration objects with isotonic and sigmoid
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n_samples = 100
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X, y = data
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sample_weight = np.random.RandomState(seed=42).uniform(size=y.size)
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X -= X.min() # MultinomialNB only allows positive X
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# split train and test
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X_train, y_train, sw_train = \
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X[:n_samples], y[:n_samples], sample_weight[:n_samples]
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X_test, y_test = X[n_samples:], y[n_samples:]
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# Naive-Bayes
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clf = MultinomialNB().fit(X_train, y_train, sample_weight=sw_train)
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prob_pos_clf = clf.predict_proba(X_test)[:, 1]
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cal_clf = CalibratedClassifierCV(clf, cv=y.size + 1, ensemble=ensemble)
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assert_raises(ValueError, cal_clf.fit, X, y)
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# Naive Bayes with calibration
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for this_X_train, this_X_test in [(X_train, X_test),
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(sparse.csr_matrix(X_train),
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sparse.csr_matrix(X_test))]:
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cal_clf = CalibratedClassifierCV(
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clf, method=method, cv=5, ensemble=ensemble
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)
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# Note that this fit overwrites the fit on the entire training
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# set
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cal_clf.fit(this_X_train, y_train, sample_weight=sw_train)
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prob_pos_cal_clf = cal_clf.predict_proba(this_X_test)[:, 1]
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# Check that brier score has improved after calibration
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assert (brier_score_loss(y_test, prob_pos_clf) >
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brier_score_loss(y_test, prob_pos_cal_clf))
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# Check invariance against relabeling [0, 1] -> [1, 2]
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cal_clf.fit(this_X_train, y_train + 1, sample_weight=sw_train)
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prob_pos_cal_clf_relabeled = cal_clf.predict_proba(this_X_test)[:, 1]
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assert_array_almost_equal(prob_pos_cal_clf,
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prob_pos_cal_clf_relabeled)
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# Check invariance against relabeling [0, 1] -> [-1, 1]
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cal_clf.fit(this_X_train, 2 * y_train - 1, sample_weight=sw_train)
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prob_pos_cal_clf_relabeled = cal_clf.predict_proba(this_X_test)[:, 1]
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assert_array_almost_equal(prob_pos_cal_clf, prob_pos_cal_clf_relabeled)
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# Check invariance against relabeling [0, 1] -> [1, 0]
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cal_clf.fit(this_X_train, (y_train + 1) % 2, sample_weight=sw_train)
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prob_pos_cal_clf_relabeled = cal_clf.predict_proba(this_X_test)[:, 1]
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if method == "sigmoid":
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assert_array_almost_equal(prob_pos_cal_clf,
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1 - prob_pos_cal_clf_relabeled)
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else:
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# Isotonic calibration is not invariant against relabeling
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# but should improve in both cases
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assert (brier_score_loss(y_test, prob_pos_clf) >
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brier_score_loss((y_test + 1) % 2,
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prob_pos_cal_clf_relabeled))
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@pytest.mark.parametrize('ensemble', [True, False])
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def test_calibration_bad_method(data, ensemble):
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# Check only "isotonic" and "sigmoid" are accepted as methods
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X, y = data
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clf = LinearSVC()
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clf_invalid_method = CalibratedClassifierCV(
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clf, method="foo", ensemble=ensemble
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)
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with pytest.raises(ValueError):
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clf_invalid_method.fit(X, y)
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@pytest.mark.parametrize('ensemble', [True, False])
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def test_calibration_regressor(data, ensemble):
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# `base-estimator` should provide either decision_function or
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# predict_proba (most regressors, for instance, should fail)
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X, y = data
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clf_base_regressor = \
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CalibratedClassifierCV(RandomForestRegressor(), ensemble=ensemble)
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with pytest.raises(RuntimeError):
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clf_base_regressor.fit(X, y)
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def test_calibration_default_estimator(data):
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# Check base_estimator default is LinearSVC
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X, y = data
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calib_clf = CalibratedClassifierCV(cv=2)
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calib_clf.fit(X, y)
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base_est = calib_clf.calibrated_classifiers_[0].base_estimator
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assert isinstance(base_est, LinearSVC)
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@pytest.mark.parametrize('ensemble', [True, False])
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def test_calibration_cv_splitter(data, ensemble):
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# Check when `cv` is a CV splitter
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X, y = data
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splits = 5
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kfold = KFold(n_splits=splits)
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calib_clf = CalibratedClassifierCV(cv=kfold, ensemble=ensemble)
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assert isinstance(calib_clf.cv, KFold)
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assert calib_clf.cv.n_splits == splits
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calib_clf.fit(X, y)
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expected_n_clf = splits if ensemble else 1
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assert len(calib_clf.calibrated_classifiers_) == expected_n_clf
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@pytest.mark.parametrize('method', ['sigmoid', 'isotonic'])
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@pytest.mark.parametrize('ensemble', [True, False])
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def test_sample_weight(data, method, ensemble):
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n_samples = 100
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X, y = data
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sample_weight = np.random.RandomState(seed=42).uniform(size=len(y))
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X_train, y_train, sw_train = \
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X[:n_samples], y[:n_samples], sample_weight[:n_samples]
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X_test = X[n_samples:]
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base_estimator = LinearSVC(random_state=42)
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calibrated_clf = CalibratedClassifierCV(
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base_estimator, method=method, ensemble=ensemble
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)
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calibrated_clf.fit(X_train, y_train, sample_weight=sw_train)
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probs_with_sw = calibrated_clf.predict_proba(X_test)
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# As the weights are used for the calibration, they should still yield
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# different predictions
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calibrated_clf.fit(X_train, y_train)
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probs_without_sw = calibrated_clf.predict_proba(X_test)
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diff = np.linalg.norm(probs_with_sw - probs_without_sw)
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assert diff > 0.1
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@pytest.mark.parametrize('method', ['sigmoid', 'isotonic'])
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@pytest.mark.parametrize('ensemble', [True, False])
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def test_parallel_execution(data, method, ensemble):
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"""Test parallel calibration"""
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X, y = data
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X_train, X_test, y_train, y_test = train_test_split(X, y, random_state=42)
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base_estimator = LinearSVC(random_state=42)
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cal_clf_parallel = CalibratedClassifierCV(
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base_estimator, method=method, n_jobs=2, ensemble=ensemble
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)
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cal_clf_parallel.fit(X_train, y_train)
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probs_parallel = cal_clf_parallel.predict_proba(X_test)
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cal_clf_sequential = CalibratedClassifierCV(
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base_estimator, method=method, n_jobs=1, ensemble=ensemble
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)
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cal_clf_sequential.fit(X_train, y_train)
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probs_sequential = cal_clf_sequential.predict_proba(X_test)
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assert_allclose(probs_parallel, probs_sequential)
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@pytest.mark.parametrize('method', ['sigmoid', 'isotonic'])
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@pytest.mark.parametrize('ensemble', [True, False])
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# increase the number of RNG seeds to assess the statistical stability of this
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# test:
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@pytest.mark.parametrize('seed', range(2))
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def test_calibration_multiclass(method, ensemble, seed):
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def multiclass_brier(y_true, proba_pred, n_classes):
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Y_onehot = np.eye(n_classes)[y_true]
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return np.sum((Y_onehot - proba_pred) ** 2) / Y_onehot.shape[0]
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# Test calibration for multiclass with classifier that implements
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# only decision function.
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clf = LinearSVC(random_state=7)
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X, y = make_blobs(n_samples=500, n_features=100, random_state=seed,
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centers=10, cluster_std=15.0)
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# Use an unbalanced dataset by collapsing 8 clusters into one class
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# to make the naive calibration based on a softmax more unlikely
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# to work.
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y[y > 2] = 2
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n_classes = np.unique(y).shape[0]
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X_train, y_train = X[::2], y[::2]
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X_test, y_test = X[1::2], y[1::2]
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clf.fit(X_train, y_train)
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cal_clf = CalibratedClassifierCV(
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clf, method=method, cv=5, ensemble=ensemble
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)
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cal_clf.fit(X_train, y_train)
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probas = cal_clf.predict_proba(X_test)
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# Check probabilities sum to 1
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assert_allclose(np.sum(probas, axis=1), np.ones(len(X_test)))
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# Check that the dataset is not too trivial, otherwise it's hard
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# to get interesting calibration data during the internal
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# cross-validation loop.
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assert 0.65 < clf.score(X_test, y_test) < 0.95
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# Check that the accuracy of the calibrated model is never degraded
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# too much compared to the original classifier.
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assert cal_clf.score(X_test, y_test) > 0.95 * clf.score(X_test, y_test)
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# Check that Brier loss of calibrated classifier is smaller than
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# loss obtained by naively turning OvR decision function to
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# probabilities via a softmax
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uncalibrated_brier = \
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multiclass_brier(y_test, softmax(clf.decision_function(X_test)),
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n_classes=n_classes)
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calibrated_brier = multiclass_brier(y_test, probas,
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n_classes=n_classes)
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assert calibrated_brier < 1.1 * uncalibrated_brier
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# Test that calibration of a multiclass classifier decreases log-loss
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# for RandomForestClassifier
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clf = RandomForestClassifier(n_estimators=30, random_state=42)
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clf.fit(X_train, y_train)
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clf_probs = clf.predict_proba(X_test)
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uncalibrated_brier = multiclass_brier(y_test, clf_probs,
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n_classes=n_classes)
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cal_clf = CalibratedClassifierCV(
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clf, method=method, cv=5, ensemble=ensemble
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)
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cal_clf.fit(X_train, y_train)
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cal_clf_probs = cal_clf.predict_proba(X_test)
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calibrated_brier = multiclass_brier(y_test, cal_clf_probs,
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n_classes=n_classes)
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assert calibrated_brier < 1.1 * uncalibrated_brier
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def test_calibration_prefit():
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"""Test calibration for prefitted classifiers"""
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n_samples = 50
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X, y = make_classification(n_samples=3 * n_samples, n_features=6,
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random_state=42)
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sample_weight = np.random.RandomState(seed=42).uniform(size=y.size)
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X -= X.min() # MultinomialNB only allows positive X
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# split train and test
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X_train, y_train, sw_train = \
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X[:n_samples], y[:n_samples], sample_weight[:n_samples]
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X_calib, y_calib, sw_calib = \
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X[n_samples:2 * n_samples], y[n_samples:2 * n_samples], \
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sample_weight[n_samples:2 * n_samples]
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X_test, y_test = X[2 * n_samples:], y[2 * n_samples:]
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# Naive-Bayes
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clf = MultinomialNB()
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# Check error if clf not prefit
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unfit_clf = CalibratedClassifierCV(clf, cv="prefit")
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with pytest.raises(NotFittedError):
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unfit_clf.fit(X_calib, y_calib)
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clf.fit(X_train, y_train, sw_train)
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prob_pos_clf = clf.predict_proba(X_test)[:, 1]
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# Naive Bayes with calibration
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for this_X_calib, this_X_test in [(X_calib, X_test),
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(sparse.csr_matrix(X_calib),
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sparse.csr_matrix(X_test))]:
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for method in ['isotonic', 'sigmoid']:
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cal_clf = CalibratedClassifierCV(clf, method=method, cv="prefit")
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for sw in [sw_calib, None]:
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cal_clf.fit(this_X_calib, y_calib, sample_weight=sw)
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y_prob = cal_clf.predict_proba(this_X_test)
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y_pred = cal_clf.predict(this_X_test)
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prob_pos_cal_clf = y_prob[:, 1]
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assert_array_equal(y_pred,
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np.array([0, 1])[np.argmax(y_prob, axis=1)])
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assert (brier_score_loss(y_test, prob_pos_clf) >
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brier_score_loss(y_test, prob_pos_cal_clf))
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@pytest.mark.parametrize('method', ['sigmoid', 'isotonic'])
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def test_calibration_ensemble_false(data, method):
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# Test that `ensemble=False` is the same as using predictions from
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# `cross_val_predict` to train calibrator.
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X, y = data
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clf = LinearSVC(random_state=7)
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cal_clf = CalibratedClassifierCV(clf, method=method, cv=3, ensemble=False)
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cal_clf.fit(X, y)
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cal_probas = cal_clf.predict_proba(X)
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# Get probas manually
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unbiased_preds = cross_val_predict(
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clf, X, y, cv=3, method='decision_function'
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)
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if method == 'isotonic':
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calibrator = IsotonicRegression(out_of_bounds='clip')
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else:
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calibrator = _SigmoidCalibration()
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calibrator.fit(unbiased_preds, y)
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# Use `clf` fit on all data
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clf.fit(X, y)
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clf_df = clf.decision_function(X)
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manual_probas = calibrator.predict(clf_df)
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assert_allclose(cal_probas[:, 1], manual_probas)
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def test_sigmoid_calibration():
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"""Test calibration values with Platt sigmoid model"""
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exF = np.array([5, -4, 1.0])
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exY = np.array([1, -1, -1])
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# computed from my python port of the C++ code in LibSVM
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AB_lin_libsvm = np.array([-0.20261354391187855, 0.65236314980010512])
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assert_array_almost_equal(AB_lin_libsvm,
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_sigmoid_calibration(exF, exY), 3)
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lin_prob = 1. / (1. + np.exp(AB_lin_libsvm[0] * exF + AB_lin_libsvm[1]))
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sk_prob = _SigmoidCalibration().fit(exF, exY).predict(exF)
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assert_array_almost_equal(lin_prob, sk_prob, 6)
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# check that _SigmoidCalibration().fit only accepts 1d array or 2d column
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# arrays
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assert_raises(ValueError, _SigmoidCalibration().fit,
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np.vstack((exF, exF)), exY)
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def test_calibration_curve():
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"""Check calibration_curve function"""
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y_true = np.array([0, 0, 0, 1, 1, 1])
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y_pred = np.array([0., 0.1, 0.2, 0.8, 0.9, 1.])
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prob_true, prob_pred = calibration_curve(y_true, y_pred, n_bins=2)
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prob_true_unnormalized, prob_pred_unnormalized = \
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calibration_curve(y_true, y_pred * 2, n_bins=2, normalize=True)
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assert len(prob_true) == len(prob_pred)
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assert len(prob_true) == 2
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assert_almost_equal(prob_true, [0, 1])
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assert_almost_equal(prob_pred, [0.1, 0.9])
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assert_almost_equal(prob_true, prob_true_unnormalized)
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assert_almost_equal(prob_pred, prob_pred_unnormalized)
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# probabilities outside [0, 1] should not be accepted when normalize
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# is set to False
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assert_raises(ValueError, calibration_curve, [1.1], [-0.1],
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normalize=False)
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# test that quantiles work as expected
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y_true2 = np.array([0, 0, 0, 0, 1, 1])
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y_pred2 = np.array([0., 0.1, 0.2, 0.5, 0.9, 1.])
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prob_true_quantile, prob_pred_quantile = calibration_curve(
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y_true2, y_pred2, n_bins=2, strategy='quantile')
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assert len(prob_true_quantile) == len(prob_pred_quantile)
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assert len(prob_true_quantile) == 2
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assert_almost_equal(prob_true_quantile, [0, 2 / 3])
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assert_almost_equal(prob_pred_quantile, [0.1, 0.8])
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# Check that error is raised when invalid strategy is selected
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assert_raises(ValueError, calibration_curve, y_true2, y_pred2,
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strategy='percentile')
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@pytest.mark.parametrize('ensemble', [True, False])
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def test_calibration_nan_imputer(ensemble):
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"""Test that calibration can accept nan"""
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X, y = make_classification(n_samples=10, n_features=2,
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n_informative=2, n_redundant=0,
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random_state=42)
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X[0, 0] = np.nan
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clf = Pipeline(
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[('imputer', SimpleImputer()),
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('rf', RandomForestClassifier(n_estimators=1))])
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clf_c = CalibratedClassifierCV(
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clf, cv=2, method='isotonic', ensemble=ensemble
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)
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|
clf_c.fit(X, y)
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clf_c.predict(X)
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|
|
|
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@pytest.mark.parametrize('ensemble', [True, False])
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|
def test_calibration_prob_sum(ensemble):
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# Test that sum of probabilities is 1. A non-regression test for
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# issue #7796
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num_classes = 2
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X, y = make_classification(n_samples=10, n_features=5,
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|
n_classes=num_classes)
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clf = LinearSVC(C=1.0, random_state=7)
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|
clf_prob = CalibratedClassifierCV(
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|
clf, method="sigmoid", cv=LeaveOneOut(), ensemble=ensemble
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|
)
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|
clf_prob.fit(X, y)
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|
|
|
probs = clf_prob.predict_proba(X)
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assert_array_almost_equal(probs.sum(axis=1), np.ones(probs.shape[0]))
|
|
|
|
|
|
@pytest.mark.parametrize('ensemble', [True, False])
|
|
def test_calibration_less_classes(ensemble):
|
|
# Test to check calibration works fine when train set in a test-train
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|
# split does not contain all classes
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|
# Since this test uses LOO, at each iteration train set will not contain a
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|
# class label
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|
X = np.random.randn(10, 5)
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|
y = np.arange(10)
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|
clf = LinearSVC(C=1.0, random_state=7)
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|
cal_clf = CalibratedClassifierCV(
|
|
clf, method="sigmoid", cv=LeaveOneOut(), ensemble=ensemble
|
|
)
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|
cal_clf.fit(X, y)
|
|
|
|
for i, calibrated_classifier in \
|
|
enumerate(cal_clf.calibrated_classifiers_):
|
|
proba = calibrated_classifier.predict_proba(X)
|
|
if ensemble:
|
|
# Check that the unobserved class has proba=0
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|
assert_array_equal(proba[:, i], np.zeros(len(y)))
|
|
# Check for all other classes proba>0
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|
assert np.all(proba[:, :i] > 0)
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|
assert np.all(proba[:, i + 1:] > 0)
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|
else:
|
|
# Check `proba` are all 1/n_classes
|
|
assert np.allclose(proba, 1 / proba.shape[0])
|
|
|
|
|
|
@ignore_warnings(category=FutureWarning)
|
|
@pytest.mark.parametrize('X', [np.random.RandomState(42).randn(15, 5, 2),
|
|
np.random.RandomState(42).randn(15, 5, 2, 6)])
|
|
def test_calibration_accepts_ndarray(X):
|
|
"""Test that calibration accepts n-dimensional arrays as input"""
|
|
y = [1, 0, 0, 1, 1, 0, 1, 1, 0, 0, 1, 0, 0, 1, 0]
|
|
|
|
class MockTensorClassifier(BaseEstimator):
|
|
"""A toy estimator that accepts tensor inputs"""
|
|
|
|
def fit(self, X, y):
|
|
self.classes_ = np.unique(y)
|
|
return self
|
|
|
|
def decision_function(self, X):
|
|
# toy decision function that just needs to have the right shape:
|
|
return X.reshape(X.shape[0], -1).sum(axis=1)
|
|
|
|
calibrated_clf = CalibratedClassifierCV(MockTensorClassifier())
|
|
# we should be able to fit this classifier with no error
|
|
calibrated_clf.fit(X, y)
|
|
|
|
|
|
@pytest.fixture
|
|
def text_data():
|
|
text_data = [
|
|
{'state': 'NY', 'age': 'adult'},
|
|
{'state': 'TX', 'age': 'adult'},
|
|
{'state': 'VT', 'age': 'child'},
|
|
]
|
|
text_labels = [1, 0, 1]
|
|
return text_data, text_labels
|
|
|
|
|
|
@pytest.fixture
|
|
def text_data_pipeline(text_data):
|
|
X, y = text_data
|
|
pipeline_prefit = Pipeline([
|
|
('vectorizer', DictVectorizer()),
|
|
('clf', RandomForestClassifier())
|
|
])
|
|
return pipeline_prefit.fit(X, y)
|
|
|
|
|
|
def test_calibration_pipeline(text_data, text_data_pipeline):
|
|
# Test that calibration works in prefit pipeline with transformer,
|
|
# where `X` is not array-like, sparse matrix or dataframe at the start.
|
|
# See https://github.com/scikit-learn/scikit-learn/issues/8710
|
|
X, y = text_data
|
|
clf = text_data_pipeline
|
|
calib_clf = CalibratedClassifierCV(clf, cv='prefit')
|
|
calib_clf.fit(X, y)
|
|
# Check attributes are obtained from fitted estimator
|
|
assert_array_equal(calib_clf.classes_, clf.classes_)
|
|
msg = "'CalibratedClassifierCV' object has no attribute"
|
|
with pytest.raises(AttributeError, match=msg):
|
|
calib_clf.n_features_in_
|
|
|
|
|
|
@pytest.mark.parametrize('clf, cv', [
|
|
pytest.param(LinearSVC(C=1), 2),
|
|
pytest.param(LinearSVC(C=1), 'prefit'),
|
|
])
|
|
def test_calibration_attributes(clf, cv):
|
|
# Check that `n_features_in_` and `classes_` attributes created properly
|
|
X, y = make_classification(n_samples=10, n_features=5,
|
|
n_classes=2, random_state=7)
|
|
if cv == 'prefit':
|
|
clf = clf.fit(X, y)
|
|
calib_clf = CalibratedClassifierCV(clf, cv=cv)
|
|
calib_clf.fit(X, y)
|
|
|
|
if cv == 'prefit':
|
|
assert_array_equal(calib_clf.classes_, clf.classes_)
|
|
assert calib_clf.n_features_in_ == clf.n_features_in_
|
|
else:
|
|
classes = LabelEncoder().fit(y).classes_
|
|
assert_array_equal(calib_clf.classes_, classes)
|
|
assert calib_clf.n_features_in_ == X.shape[1]
|
|
|
|
|
|
# FIXME: remove in 1.1
|
|
def test_calibrated_classifier_cv_deprecation(data):
|
|
# Check that we raise the proper deprecation warning if accessing
|
|
# `calibrators_` from the `_CalibratedClassifier`.
|
|
X, y = data
|
|
calib_clf = CalibratedClassifierCV(cv=2).fit(X, y)
|
|
|
|
with pytest.warns(FutureWarning):
|
|
calibrators = calib_clf.calibrated_classifiers_[0].calibrators_
|
|
|
|
for clf1, clf2 in zip(
|
|
calibrators, calib_clf.calibrated_classifiers_[0].calibrators
|
|
):
|
|
assert clf1 is clf2
|