下面使用經典的20類新聞文本作爲試驗數據：
Python源碼：
#coding=utf-8
#load news data
from sklearn.datasets import fetch_20newsgroups
#-------------
from sklearn.cross_validation import train_test_split
#-------------
from sklearn.feature_extraction.text import CountVectorizer
#-------------
from sklearn.naive_bayes import MultinomialNB
#-------------
from sklearn.metrics import classification_report
#-------------download data
news=fetch_20newsgroups(subset='all')
print len(news.data)
print news.data[0]
#-------------split data
#75% training set,25% testing set
X_train,X_test,y_train,y_test=train_test_split(news.data,news.target,test_size=0.25,random_state=33)
#-------------transfer data to vector
vec=CountVectorizer()
X_train=vec.fit_transform(X_train)
#X_test=vec.fit_transform(X_test) raise ValueError('dimension mismatch')
vectorizer_test = CountVectorizer(vocabulary=vec.vocabulary_)
X_test = vectorizer_test.transform(X_test)
#-------------training
#initialize NB model with default config
mnb=MultinomialNB()
#training model
mnb.fit(X_train,y_train)
#run on test data
y_predict=mnb.predict(X_test)
#-------------performance
print 'The Accuracy is',mnb.score(X_test,y_test)
print classification_report(y_test,y_predict,target_names=news.target_names)18846
From: Mamatha Devineni Ratnam <[email protected]>
Subject: Pens fans reactions
Organization: Post Office, Carnegie Mellon, Pittsburgh, PA
Lines: 12
NNTP-Posting-Host: po4.andrew.cmu.edu
I am sure some bashers of Pens fans are pretty confused about the lack
of any kind of posts about the recent Pens massacre of the Devils. Actually,
I am bit puzzled too and a bit relieved. However, I am going to put an end
to non-PIttsburghers' relief with a bit of praise for the Pens. Man, they
are killing those Devils worse than I thought. Jagr just showed you why
he is much better than his regular season stats. He is also a lot
fo fun to watch in the playoffs. Bowman should let JAgr have a lot of
fun in the next couple of games since the Pens are going to beat the pulp out of Jersey anyway. I was very disappointed not to see the Islanders lose the final
regular season game. PENS RULE!!!
The Accuracy is 0.839770797963
precision recall f1-score support
alt.atheism 0.86 0.86 0.86 201
comp.graphics 0.59 0.86 0.70 250
comp.os.ms-windows.misc 0.89 0.10 0.17 248
comp.sys.ibm.pc.hardware 0.60 0.88 0.72 240
comp.sys.mac.hardware 0.93 0.78 0.85 242
comp.windows.x 0.82 0.84 0.83 263
misc.forsale 0.91 0.70 0.79 257
rec.autos 0.89 0.89 0.89 238
rec.motorcycles 0.98 0.92 0.95 276
rec.sport.baseball 0.98 0.91 0.95 251
rec.sport.hockey 0.93 0.99 0.96 233
sci.crypt 0.86 0.98 0.91 238
sci.electronics 0.85 0.88 0.86 249
sci.med 0.92 0.94 0.93 245
sci.space 0.89 0.96 0.92 221
soc.religion.christian 0.78 0.96 0.86 232
talk.politics.guns 0.88 0.96 0.92 251
talk.politics.mideast 0.90 0.98 0.94 231
talk.politics.misc 0.79 0.89 0.84 188
talk.religion.misc 0.93 0.44 0.60 158
avg / total 0.86 0.84 0.82 4712