# 分类特征稀疏的文本 >翻译者:[@Loopy](https://github.com/loopyme) >校验者:[@barrycg](https://github.com/barrycg) 这个例子展示了如何使用scikit-learn中的单词包方法,根据主题对文档进行分类。本例使用scipy.sparse中的矩阵来存储特征,并演示各种能够有效处理稀疏矩阵的分类器。 本例中使用的数据集是20条新闻组数据集。通过scikit-learn可以自动下载该数据集,并进行缓存。 下述条形图展示了各个不同分类器,其信息包括精度、训练时间(已归一化)和测试时间(已归一化)。 ```python 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 SelectFromModel 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, ComplementNB, 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 ``` ```python # 在stdout上显示进度日志 logging.basicConfig(level=logging.INFO,format='%(asctime)s %(levelname)s %(message)s') ``` ```python # 解析命令行参数 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.") ```