def test_sparse_tf_idf():
hv = SparseHashingVectorizer(dim=1000000, probes=3)
hv.vectorize(JUNK_FOOD_DOCS)
hv.vectorize(NOTJUNK_FOOD_DOCS)
# extract the TF-IDF data
X = hv.get_tfidf()
assert_equal(X.shape, (11, 1000000))
# label junk food as -1, the others as +1
y = np.ones(X.shape[0])
y[:6] = -1
# train and test a classifier
clf = SVC(kernel='linear', C=10).fit(X[1:-1], y[1:-1])
assert_equal(clf.predict(X[0, :]), [-1])
assert_equal(clf.predict(X[-1, :]), [1])
print "news_train.data is sparse: ",
print sp.issparse(news_train.data)
# The documents have been hashed into TF-IDF (Term Frequencies times Inverse
# Document Frequencies) vectors of a fixed dimension.
print "n_samples: %d, n_features: %d" % news_train.data.shape
print "Training a linear SVM (hinge loss and L2 regularizer)..."
parameters = {
'kernel': 'linear',
'C': 10,
}
print "parameters:", parameters
t0 = time()
clf = SVC(**parameters).fit(news_train.data, news_train.target)
print "done in %fs" % (time() - t0)
print "Percentage of non zeros coef: %f" % (np.mean(clf.coef_ != 0) * 100)
print "Loading 20 newsgroups test set... "
t0 = time()
news_test = load_mlcomp('20news-18828', 'test', sparse=True)
print "done in %fs" % (time() - t0)
print "Predicting the labels of the test set..."
t0 = time()
pred = clf.predict(news_test.data)
print "done in %fs" % (time() - t0)
print "Classification accuracy: %f" % (np.mean(pred == news_test.target) * 100)
cm = confusion_matrix(news_test.target, pred)
