.. _sphx_glr_auto_examples_text_document_classification_20newsgroups.py: ====================================================== Classification of text documents using sparse features ====================================================== This is an example showing how scikit-learn can be used to classify documents by topics using a bag-of-words approach. This example uses a scipy.sparse matrix to store the features and demonstrates various classifiers that can efficiently handle sparse matrices. The dataset used in this example is the 20 newsgroups dataset. It will be automatically downloaded, then cached. The bar plot indicates the accuracy, training time (normalized) and test time (normalized) of each classifier. .. code-block:: python # Author: Peter Prettenhofer # Olivier Grisel # Mathieu Blondel # Lars Buitinck # License: BSD 3 clause from __future__ import print_function import logging import numpy as np from optparse import OptionParser import sys from time import time import matplotlib.pyplot as plt from sklearn.datasets import fetch_20newsgroups from sklearn.feature_extraction.text import TfidfVectorizer from sklearn.feature_extraction.text import HashingVectorizer from sklearn.feature_selection import SelectKBest, chi2 from sklearn.linear_model import RidgeClassifier from sklearn.pipeline import Pipeline from sklearn.svm import LinearSVC from sklearn.linear_model import SGDClassifier from sklearn.linear_model import Perceptron from sklearn.linear_model import PassiveAggressiveClassifier from sklearn.naive_bayes import BernoulliNB, MultinomialNB from sklearn.neighbors import KNeighborsClassifier from sklearn.neighbors import NearestCentroid from sklearn.ensemble import RandomForestClassifier from sklearn.utils.extmath import density from sklearn import metrics # Display progress logs on stdout logging.basicConfig(level=logging.INFO, format='%(asctime)s %(levelname)s %(message)s') # parse commandline arguments op = OptionParser() op.add_option("--report", action="store_true", dest="print_report", help="Print a detailed classification report.") op.add_option("--chi2_select", action="store", type="int", dest="select_chi2", help="Select some number of features using a chi-squared test") op.add_option("--confusion_matrix", action="store_true", dest="print_cm", help="Print the confusion matrix.") op.add_option("--top10", action="store_true", dest="print_top10", help="Print ten most discriminative terms per class" " for every classifier.") op.add_option("--all_categories", action="store_true", dest="all_categories", help="Whether to use all categories or not.") op.add_option("--use_hashing", action="store_true", help="Use a hashing vectorizer.") op.add_option("--n_features", action="store", type=int, default=2 ** 16, help="n_features when using the hashing vectorizer.") op.add_option("--filtered", action="store_true", help="Remove newsgroup information that is easily overfit: " "headers, signatures, and quoting.") (opts, args) = op.parse_args() if len(args) > 0: op.error("this script takes no arguments.") sys.exit(1) print(__doc__) op.print_help() print() Load some categories from the training set .. code-block:: python if opts.all_categories: categories = None else: categories = [ 'alt.atheism', 'talk.religion.misc', 'comp.graphics', 'sci.space', ] if opts.filtered: remove = ('headers', 'footers', 'quotes') else: remove = () print("Loading 20 newsgroups dataset for categories:") print(categories if categories else "all") data_train = fetch_20newsgroups(subset='train', categories=categories, shuffle=True, random_state=42, remove=remove) data_test = fetch_20newsgroups(subset='test', categories=categories, shuffle=True, random_state=42, remove=remove) print('data loaded') # order of labels in `target_names` can be different from `categories` target_names = data_train.target_names def size_mb(docs): return sum(len(s.encode('utf-8')) for s in docs) / 1e6 data_train_size_mb = size_mb(data_train.data) data_test_size_mb = size_mb(data_test.data) print("%d documents - %0.3fMB (training set)" % ( len(data_train.data), data_train_size_mb)) print("%d documents - %0.3fMB (test set)" % ( len(data_test.data), data_test_size_mb)) print("%d categories" % len(categories)) print() # split a training set and a test set y_train, y_test = data_train.target, data_test.target print("Extracting features from the training data using a sparse vectorizer") t0 = time() if opts.use_hashing: vectorizer = HashingVectorizer(stop_words='english', non_negative=True, n_features=opts.n_features) X_train = vectorizer.transform(data_train.data) else: vectorizer = TfidfVectorizer(sublinear_tf=True, max_df=0.5, stop_words='english') X_train = vectorizer.fit_transform(data_train.data) duration = time() - t0 print("done in %fs at %0.3fMB/s" % (duration, data_train_size_mb / duration)) print("n_samples: %d, n_features: %d" % X_train.shape) print() print("Extracting features from the test data using the same vectorizer") t0 = time() X_test = vectorizer.transform(data_test.data) duration = time() - t0 print("done in %fs at %0.3fMB/s" % (duration, data_test_size_mb / duration)) print("n_samples: %d, n_features: %d" % X_test.shape) print() # mapping from integer feature name to original token string if opts.use_hashing: feature_names = None else: feature_names = vectorizer.get_feature_names() if opts.select_chi2: print("Extracting %d best features by a chi-squared test" % opts.select_chi2) t0 = time() ch2 = SelectKBest(chi2, k=opts.select_chi2) X_train = ch2.fit_transform(X_train, y_train) X_test = ch2.transform(X_test) if feature_names: # keep selected feature names feature_names = [feature_names[i] for i in ch2.get_support(indices=True)] print("done in %fs" % (time() - t0)) print() if feature_names: feature_names = np.asarray(feature_names) def trim(s): """Trim string to fit on terminal (assuming 80-column display)""" return s if len(s) <= 80 else s[:77] + "..." Benchmark classifiers .. code-block:: python def benchmark(clf): print('_' * 80) print("Training: ") print(clf) t0 = time() clf.fit(X_train, y_train) train_time = time() - t0 print("train time: %0.3fs" % train_time) t0 = time() pred = clf.predict(X_test) test_time = time() - t0 print("test time: %0.3fs" % test_time) score = metrics.accuracy_score(y_test, pred) print("accuracy: %0.3f" % score) if hasattr(clf, 'coef_'): print("dimensionality: %d" % clf.coef_.shape[1]) print("density: %f" % density(clf.coef_)) if opts.print_top10 and feature_names is not None: print("top 10 keywords per class:") for i, label in enumerate(target_names): top10 = np.argsort(clf.coef_[i])[-10:] print(trim("%s: %s" % (label, " ".join(feature_names[top10])))) print() if opts.print_report: print("classification report:") print(metrics.classification_report(y_test, pred, target_names=target_names)) if opts.print_cm: print("confusion matrix:") print(metrics.confusion_matrix(y_test, pred)) print() clf_descr = str(clf).split('(')[0] return clf_descr, score, train_time, test_time results = [] for clf, name in ( (RidgeClassifier(tol=1e-2, solver="lsqr"), "Ridge Classifier"), (Perceptron(n_iter=50), "Perceptron"), (PassiveAggressiveClassifier(n_iter=50), "Passive-Aggressive"), (KNeighborsClassifier(n_neighbors=10), "kNN"), (RandomForestClassifier(n_estimators=100), "Random forest")): print('=' * 80) print(name) results.append(benchmark(clf)) for penalty in ["l2", "l1"]: print('=' * 80) print("%s penalty" % penalty.upper()) # Train Liblinear model results.append(benchmark(LinearSVC(loss='l2', penalty=penalty, dual=False, tol=1e-3))) # Train SGD model results.append(benchmark(SGDClassifier(alpha=.0001, n_iter=50, penalty=penalty))) # Train SGD with Elastic Net penalty print('=' * 80) print("Elastic-Net penalty") results.append(benchmark(SGDClassifier(alpha=.0001, n_iter=50, penalty="elasticnet"))) # Train NearestCentroid without threshold print('=' * 80) print("NearestCentroid (aka Rocchio classifier)") results.append(benchmark(NearestCentroid())) # Train sparse Naive Bayes classifiers print('=' * 80) print("Naive Bayes") results.append(benchmark(MultinomialNB(alpha=.01))) results.append(benchmark(BernoulliNB(alpha=.01))) print('=' * 80) print("LinearSVC with L1-based feature selection") # The smaller C, the stronger the regularization. # The more regularization, the more sparsity. results.append(benchmark(Pipeline([ ('feature_selection', LinearSVC(penalty="l1", dual=False, tol=1e-3)), ('classification', LinearSVC()) ]))) # make some plots indices = np.arange(len(results)) results = [[x[i] for x in results] for i in range(4)] clf_names, score, training_time, test_time = results training_time = np.array(training_time) / np.max(training_time) test_time = np.array(test_time) / np.max(test_time) plt.figure(figsize=(12, 8)) plt.title("Score") plt.barh(indices, score, .2, label="score", color='navy') plt.barh(indices + .3, training_time, .2, label="training time", color='c') plt.barh(indices + .6, test_time, .2, label="test time", color='darkorange') plt.yticks(()) plt.legend(loc='best') plt.subplots_adjust(left=.25) plt.subplots_adjust(top=.95) plt.subplots_adjust(bottom=.05) for i, c in zip(indices, clf_names): plt.text(-.3, i, c) plt.show() **Total running time of the script:** (0 minutes 0.000 seconds) .. container:: sphx-glr-download **Download Python source code:** :download:`document_classification_20newsgroups.py ` .. container:: sphx-glr-download **Download IPython notebook:** :download:`document_classification_20newsgroups.ipynb `