/usr/lib/python3/dist-packages/sklearn/tests/test_naive_bayes.py is in python3-sklearn 0.17.0-4.
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from io import BytesIO
import numpy as np
import scipy.sparse
from sklearn.datasets import load_digits, load_iris
from sklearn.cross_validation import cross_val_score, train_test_split
from sklearn.externals.six.moves import zip
from sklearn.utils.testing import assert_almost_equal
from sklearn.utils.testing import assert_array_equal
from sklearn.utils.testing import assert_array_almost_equal
from sklearn.utils.testing import assert_equal
from sklearn.utils.testing import assert_raises
from sklearn.utils.testing import assert_greater
from sklearn.naive_bayes import GaussianNB, BernoulliNB, MultinomialNB
# Data is just 6 separable points in the plane
X = np.array([[-2, -1], [-1, -1], [-1, -2], [1, 1], [1, 2], [2, 1]])
y = np.array([1, 1, 1, 2, 2, 2])
# A bit more random tests
rng = np.random.RandomState(0)
X1 = rng.normal(size=(10, 3))
y1 = (rng.normal(size=(10)) > 0).astype(np.int)
# Data is 6 random integer points in a 100 dimensional space classified to
# three classes.
X2 = rng.randint(5, size=(6, 100))
y2 = np.array([1, 1, 2, 2, 3, 3])
def test_gnb():
# Gaussian Naive Bayes classification.
# This checks that GaussianNB implements fit and predict and returns
# correct values for a simple toy dataset.
clf = GaussianNB()
y_pred = clf.fit(X, y).predict(X)
assert_array_equal(y_pred, y)
y_pred_proba = clf.predict_proba(X)
y_pred_log_proba = clf.predict_log_proba(X)
assert_array_almost_equal(np.log(y_pred_proba), y_pred_log_proba, 8)
# Test whether label mismatch between target y and classes raises
# an Error
# FIXME Remove this test once the more general partial_fit tests are merged
assert_raises(ValueError, GaussianNB().partial_fit, X, y, classes=[0, 1])
def test_gnb_prior():
# Test whether class priors are properly set.
clf = GaussianNB().fit(X, y)
assert_array_almost_equal(np.array([3, 3]) / 6.0,
clf.class_prior_, 8)
clf.fit(X1, y1)
# Check that the class priors sum to 1
assert_array_almost_equal(clf.class_prior_.sum(), 1)
def test_gnb_sample_weight():
"""Test whether sample weights are properly used in GNB. """
# Sample weights all being 1 should not change results
sw = np.ones(6)
clf = GaussianNB().fit(X, y)
clf_sw = GaussianNB().fit(X, y, sw)
assert_array_almost_equal(clf.theta_, clf_sw.theta_)
assert_array_almost_equal(clf.sigma_, clf_sw.sigma_)
# Fitting twice with half sample-weights should result
# in same result as fitting once with full weights
sw = rng.rand(y.shape[0])
clf1 = GaussianNB().fit(X, y, sample_weight=sw)
clf2 = GaussianNB().partial_fit(X, y, classes=[1, 2], sample_weight=sw / 2)
clf2.partial_fit(X, y, sample_weight=sw / 2)
assert_array_almost_equal(clf1.theta_, clf2.theta_)
assert_array_almost_equal(clf1.sigma_, clf2.sigma_)
# Check that duplicate entries and correspondingly increased sample
# weights yield the same result
ind = rng.randint(0, X.shape[0], 20)
sample_weight = np.bincount(ind, minlength=X.shape[0])
clf_dupl = GaussianNB().fit(X[ind], y[ind])
clf_sw = GaussianNB().fit(X, y, sample_weight)
assert_array_almost_equal(clf_dupl.theta_, clf_sw.theta_)
assert_array_almost_equal(clf_dupl.sigma_, clf_sw.sigma_)
def test_discrete_prior():
# Test whether class priors are properly set.
for cls in [BernoulliNB, MultinomialNB]:
clf = cls().fit(X2, y2)
assert_array_almost_equal(np.log(np.array([2, 2, 2]) / 6.0),
clf.class_log_prior_, 8)
def test_mnnb():
# Test Multinomial Naive Bayes classification.
# This checks that MultinomialNB implements fit and predict and returns
# correct values for a simple toy dataset.
for X in [X2, scipy.sparse.csr_matrix(X2)]:
# Check the ability to predict the learning set.
clf = MultinomialNB()
assert_raises(ValueError, clf.fit, -X, y2)
y_pred = clf.fit(X, y2).predict(X)
assert_array_equal(y_pred, y2)
# Verify that np.log(clf.predict_proba(X)) gives the same results as
# clf.predict_log_proba(X)
y_pred_proba = clf.predict_proba(X)
y_pred_log_proba = clf.predict_log_proba(X)
assert_array_almost_equal(np.log(y_pred_proba), y_pred_log_proba, 8)
# Check that incremental fitting yields the same results
clf2 = MultinomialNB()
clf2.partial_fit(X[:2], y2[:2], classes=np.unique(y2))
clf2.partial_fit(X[2:5], y2[2:5])
clf2.partial_fit(X[5:], y2[5:])
y_pred2 = clf2.predict(X)
assert_array_equal(y_pred2, y2)
y_pred_proba2 = clf2.predict_proba(X)
y_pred_log_proba2 = clf2.predict_log_proba(X)
assert_array_almost_equal(np.log(y_pred_proba2), y_pred_log_proba2, 8)
assert_array_almost_equal(y_pred_proba2, y_pred_proba)
assert_array_almost_equal(y_pred_log_proba2, y_pred_log_proba)
# Partial fit on the whole data at once should be the same as fit too
clf3 = MultinomialNB()
clf3.partial_fit(X, y2, classes=np.unique(y2))
y_pred3 = clf3.predict(X)
assert_array_equal(y_pred3, y2)
y_pred_proba3 = clf3.predict_proba(X)
y_pred_log_proba3 = clf3.predict_log_proba(X)
assert_array_almost_equal(np.log(y_pred_proba3), y_pred_log_proba3, 8)
assert_array_almost_equal(y_pred_proba3, y_pred_proba)
assert_array_almost_equal(y_pred_log_proba3, y_pred_log_proba)
def check_partial_fit(cls):
clf1 = cls()
clf1.fit([[0, 1], [1, 0]], [0, 1])
clf2 = cls()
clf2.partial_fit([[0, 1], [1, 0]], [0, 1], classes=[0, 1])
assert_array_equal(clf1.class_count_, clf2.class_count_)
assert_array_equal(clf1.feature_count_, clf2.feature_count_)
clf3 = cls()
clf3.partial_fit([[0, 1]], [0], classes=[0, 1])
clf3.partial_fit([[1, 0]], [1])
assert_array_equal(clf1.class_count_, clf3.class_count_)
assert_array_equal(clf1.feature_count_, clf3.feature_count_)
def test_discretenb_partial_fit():
for cls in [MultinomialNB, BernoulliNB]:
yield check_partial_fit, cls
def test_gnb_partial_fit():
clf = GaussianNB().fit(X, y)
clf_pf = GaussianNB().partial_fit(X, y, np.unique(y))
assert_array_almost_equal(clf.theta_, clf_pf.theta_)
assert_array_almost_equal(clf.sigma_, clf_pf.sigma_)
assert_array_almost_equal(clf.class_prior_, clf_pf.class_prior_)
clf_pf2 = GaussianNB().partial_fit(X[0::2, :], y[0::2], np.unique(y))
clf_pf2.partial_fit(X[1::2], y[1::2])
assert_array_almost_equal(clf.theta_, clf_pf2.theta_)
assert_array_almost_equal(clf.sigma_, clf_pf2.sigma_)
assert_array_almost_equal(clf.class_prior_, clf_pf2.class_prior_)
def test_discretenb_pickle():
# Test picklability of discrete naive Bayes classifiers
for cls in [BernoulliNB, MultinomialNB, GaussianNB]:
clf = cls().fit(X2, y2)
y_pred = clf.predict(X2)
store = BytesIO()
pickle.dump(clf, store)
clf = pickle.load(BytesIO(store.getvalue()))
assert_array_equal(y_pred, clf.predict(X2))
if cls is not GaussianNB:
# TODO re-enable me when partial_fit is implemented for GaussianNB
# Test pickling of estimator trained with partial_fit
clf2 = cls().partial_fit(X2[:3], y2[:3], classes=np.unique(y2))
clf2.partial_fit(X2[3:], y2[3:])
store = BytesIO()
pickle.dump(clf2, store)
clf2 = pickle.load(BytesIO(store.getvalue()))
assert_array_equal(y_pred, clf2.predict(X2))
def test_input_check_fit():
# Test input checks for the fit method
for cls in [BernoulliNB, MultinomialNB, GaussianNB]:
# check shape consistency for number of samples at fit time
assert_raises(ValueError, cls().fit, X2, y2[:-1])
# check shape consistency for number of input features at predict time
clf = cls().fit(X2, y2)
assert_raises(ValueError, clf.predict, X2[:, :-1])
def test_input_check_partial_fit():
for cls in [BernoulliNB, MultinomialNB]:
# check shape consistency
assert_raises(ValueError, cls().partial_fit, X2, y2[:-1],
classes=np.unique(y2))
# classes is required for first call to partial fit
assert_raises(ValueError, cls().partial_fit, X2, y2)
# check consistency of consecutive classes values
clf = cls()
clf.partial_fit(X2, y2, classes=np.unique(y2))
assert_raises(ValueError, clf.partial_fit, X2, y2,
classes=np.arange(42))
# check consistency of input shape for partial_fit
assert_raises(ValueError, clf.partial_fit, X2[:, :-1], y2)
# check consistency of input shape for predict
assert_raises(ValueError, clf.predict, X2[:, :-1])
def test_discretenb_predict_proba():
# Test discrete NB classes' probability scores
# The 100s below distinguish Bernoulli from multinomial.
# FIXME: write a test to show this.
X_bernoulli = [[1, 100, 0], [0, 1, 0], [0, 100, 1]]
X_multinomial = [[0, 1], [1, 3], [4, 0]]
# test binary case (1-d output)
y = [0, 0, 2] # 2 is regression test for binary case, 02e673
for cls, X in zip([BernoulliNB, MultinomialNB],
[X_bernoulli, X_multinomial]):
clf = cls().fit(X, y)
assert_equal(clf.predict(X[-1:]), 2)
assert_equal(clf.predict_proba([X[0]]).shape, (1, 2))
assert_array_almost_equal(clf.predict_proba(X[:2]).sum(axis=1),
np.array([1., 1.]), 6)
# test multiclass case (2-d output, must sum to one)
y = [0, 1, 2]
for cls, X in zip([BernoulliNB, MultinomialNB],
[X_bernoulli, X_multinomial]):
clf = cls().fit(X, y)
assert_equal(clf.predict_proba(X[0:1]).shape, (1, 3))
assert_equal(clf.predict_proba(X[:2]).shape, (2, 3))
assert_almost_equal(np.sum(clf.predict_proba([X[1]])), 1)
assert_almost_equal(np.sum(clf.predict_proba([X[-1]])), 1)
assert_almost_equal(np.sum(np.exp(clf.class_log_prior_)), 1)
assert_almost_equal(np.sum(np.exp(clf.intercept_)), 1)
def test_discretenb_uniform_prior():
# Test whether discrete NB classes fit a uniform prior
# when fit_prior=False and class_prior=None
for cls in [BernoulliNB, MultinomialNB]:
clf = cls()
clf.set_params(fit_prior=False)
clf.fit([[0], [0], [1]], [0, 0, 1])
prior = np.exp(clf.class_log_prior_)
assert_array_equal(prior, np.array([.5, .5]))
def test_discretenb_provide_prior():
# Test whether discrete NB classes use provided prior
for cls in [BernoulliNB, MultinomialNB]:
clf = cls(class_prior=[0.5, 0.5])
clf.fit([[0], [0], [1]], [0, 0, 1])
prior = np.exp(clf.class_log_prior_)
assert_array_equal(prior, np.array([.5, .5]))
# Inconsistent number of classes with prior
assert_raises(ValueError, clf.fit, [[0], [1], [2]], [0, 1, 2])
assert_raises(ValueError, clf.partial_fit, [[0], [1]], [0, 1],
classes=[0, 1, 1])
def test_discretenb_provide_prior_with_partial_fit():
# Test whether discrete NB classes use provided prior
# when using partial_fit
iris = load_iris()
iris_data1, iris_data2, iris_target1, iris_target2 = train_test_split(
iris.data, iris.target, test_size=0.4, random_state=415)
for cls in [BernoulliNB, MultinomialNB]:
for prior in [None, [0.3, 0.3, 0.4]]:
clf_full = cls(class_prior=prior)
clf_full.fit(iris.data, iris.target)
clf_partial = cls(class_prior=prior)
clf_partial.partial_fit(iris_data1, iris_target1,
classes=[0, 1, 2])
clf_partial.partial_fit(iris_data2, iris_target2)
assert_array_almost_equal(clf_full.class_log_prior_,
clf_partial.class_log_prior_)
def test_sample_weight_multiclass():
for cls in [BernoulliNB, MultinomialNB]:
# check shape consistency for number of samples at fit time
yield check_sample_weight_multiclass, cls
def check_sample_weight_multiclass(cls):
X = [
[0, 0, 1],
[0, 1, 1],
[0, 1, 1],
[1, 0, 0],
]
y = [0, 0, 1, 2]
sample_weight = np.array([1, 1, 2, 2], dtype=np.float)
sample_weight /= sample_weight.sum()
clf = cls().fit(X, y, sample_weight=sample_weight)
assert_array_equal(clf.predict(X), [0, 1, 1, 2])
# Check sample weight using the partial_fit method
clf = cls()
clf.partial_fit(X[:2], y[:2], classes=[0, 1, 2],
sample_weight=sample_weight[:2])
clf.partial_fit(X[2:3], y[2:3], sample_weight=sample_weight[2:3])
clf.partial_fit(X[3:], y[3:], sample_weight=sample_weight[3:])
assert_array_equal(clf.predict(X), [0, 1, 1, 2])
def test_sample_weight_mnb():
clf = MultinomialNB()
clf.fit([[1, 2], [1, 2], [1, 0]],
[0, 0, 1],
sample_weight=[1, 1, 4])
assert_array_equal(clf.predict([[1, 0]]), [1])
positive_prior = np.exp(clf.intercept_[0])
assert_array_almost_equal([1 - positive_prior, positive_prior],
[1 / 3., 2 / 3.])
def test_coef_intercept_shape():
# coef_ and intercept_ should have shapes as in other linear models.
# Non-regression test for issue #2127.
X = [[1, 0, 0], [1, 1, 1]]
y = [1, 2] # binary classification
for clf in [MultinomialNB(), BernoulliNB()]:
clf.fit(X, y)
assert_equal(clf.coef_.shape, (1, 3))
assert_equal(clf.intercept_.shape, (1,))
def test_check_accuracy_on_digits():
# Non regression test to make sure that any further refactoring / optim
# of the NB models do not harm the performance on a slightly non-linearly
# separable dataset
digits = load_digits()
X, y = digits.data, digits.target
binary_3v8 = np.logical_or(digits.target == 3, digits.target == 8)
X_3v8, y_3v8 = X[binary_3v8], y[binary_3v8]
# Multinomial NB
scores = cross_val_score(MultinomialNB(alpha=10), X, y, cv=10)
assert_greater(scores.mean(), 0.86)
scores = cross_val_score(MultinomialNB(alpha=10), X_3v8, y_3v8, cv=10)
assert_greater(scores.mean(), 0.94)
# Bernoulli NB
scores = cross_val_score(BernoulliNB(alpha=10), X > 4, y, cv=10)
assert_greater(scores.mean(), 0.83)
scores = cross_val_score(BernoulliNB(alpha=10), X_3v8 > 4, y_3v8, cv=10)
assert_greater(scores.mean(), 0.92)
# Gaussian NB
scores = cross_val_score(GaussianNB(), X, y, cv=10)
assert_greater(scores.mean(), 0.77)
scores = cross_val_score(GaussianNB(), X_3v8, y_3v8, cv=10)
assert_greater(scores.mean(), 0.86)
def test_feature_log_prob_bnb():
# Test for issue #4268.
# Tests that the feature log prob value computed by BernoulliNB when
# alpha=1.0 is equal to the expression given in Manning, Raghavan,
# and Schuetze's "Introduction to Information Retrieval" book:
# http://nlp.stanford.edu/IR-book/html/htmledition/the-bernoulli-model-1.html
X = np.array([[0, 0, 0], [1, 1, 0], [0, 1, 0], [1, 0, 1], [0, 1, 0]])
Y = np.array([0, 0, 1, 2, 2])
# Fit Bernoulli NB w/ alpha = 1.0
clf = BernoulliNB(alpha=1.0)
clf.fit(X, Y)
# Manually form the (log) numerator and denominator that
# constitute P(feature presence | class)
num = np.log(clf.feature_count_ + 1.0)
denom = np.tile(np.log(clf.class_count_ + 2.0), (X.shape[1], 1)).T
# Check manual estimate matches
assert_array_equal(clf.feature_log_prob_, (num - denom))
def test_bnb():
# Tests that BernoulliNB when alpha=1.0 gives the same values as
# those given for the toy example in Manning, Raghavan, and
# Schuetze's "Introduction to Information Retrieval" book:
# http://nlp.stanford.edu/IR-book/html/htmledition/the-bernoulli-model-1.html
# Training data points are:
# Chinese Beijing Chinese (class: China)
# Chinese Chinese Shanghai (class: China)
# Chinese Macao (class: China)
# Tokyo Japan Chinese (class: Japan)
# Features are Beijing, Chinese, Japan, Macao, Shanghai, and Tokyo
X = np.array([[1, 1, 0, 0, 0, 0],
[0, 1, 0, 0, 1, 0],
[0, 1, 0, 1, 0, 0],
[0, 1, 1, 0, 0, 1]])
# Classes are China (0), Japan (1)
Y = np.array([0, 0, 0, 1])
# Fit BernoulliBN w/ alpha = 1.0
clf = BernoulliNB(alpha=1.0)
clf.fit(X, Y)
# Check the class prior is correct
class_prior = np.array([0.75, 0.25])
assert_array_almost_equal(np.exp(clf.class_log_prior_), class_prior)
# Check the feature probabilities are correct
feature_prob = np.array([[0.4, 0.8, 0.2, 0.4, 0.4, 0.2],
[1/3.0, 2/3.0, 2/3.0, 1/3.0, 1/3.0, 2/3.0]])
assert_array_almost_equal(np.exp(clf.feature_log_prob_), feature_prob)
# Testing data point is:
# Chinese Chinese Chinese Tokyo Japan
X_test = np.array([[0, 1, 1, 0, 0, 1]])
# Check the predictive probabilities are correct
unnorm_predict_proba = np.array([[0.005183999999999999,
0.02194787379972565]])
predict_proba = unnorm_predict_proba / np.sum(unnorm_predict_proba)
assert_array_almost_equal(clf.predict_proba(X_test), predict_proba)
def test_naive_bayes_scale_invariance():
# Scaling the data should not change the prediction results
iris = load_iris()
X, y = iris.data, iris.target
labels = [GaussianNB().fit(f * X, y).predict(f * X)
for f in [1E-10, 1, 1E10]]
assert_array_equal(labels[0], labels[1])
assert_array_equal(labels[1], labels[2])
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