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import cPickle as pickle
import numpy as np
import scipy.sparse
from cStringIO import StringIO
from numpy.testing import assert_almost_equal
from numpy.testing import assert_array_equal
from numpy.testing import assert_array_almost_equal
from numpy.testing import assert_equal
from nose.tools import assert_raises
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)
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_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():
"""
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()
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)
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 = StringIO()
pickle.dump(clf, store)
clf = pickle.load(StringIO(store.getvalue()))
assert_array_equal(y_pred, clf.predict(X2))
def test_input_check():
"""Test input checks"""
for cls in [BernoulliNB, MultinomialNB, GaussianNB]:
clf = cls()
assert_raises(ValueError, clf.fit, X2, y2[:-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]).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()
clf.fit([[0], [0], [1]], [0, 0, 1], class_prior=[0.5, 0.5])
prior = np.exp(clf.class_log_prior_)
assert_array_equal(prior, np.array([.5, .5]))
def test_sample_weight():
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_)
assert_array_almost_equal([1 - positive_prior, positive_prior],
[1 / 3., 2 / 3.])
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