如何使用 sklearn 库对朴素贝叶斯进行文本分类？

Question

我正在尝试使用朴素贝叶斯文本分类器进行文本分类。我的数据采用以下格式，根据问题和摘录我必须决定问题的主题。训练数据有超过 20K 条记录。我知道 SVM 在这里会是更好的选择，但我想选择 Naive Bayes using sklearn library.

{[{"topic":"electronics","question":"What is the effective differencial effective of this circuit","excerpt":"I'm trying to work out, in general terms, the effective capacitance of this circuit (see diagram: http://i.stack.imgur.com/BS85b.png).  \n\nWhat is the effective capacitance of this circuit and will the ...\r\n        "},
{"topic":"electronics","question":"Outlet Installation--more wires than my new outlet can use [on hold]","excerpt":"I am replacing a wall outlet with a Cooper Wiring USB outlet (TR7745).  The new outlet has 3 wires coming out of it--a black, a white, and a green.  Each one needs to be attached with a wire nut to ...\r\n        "}]}

这是我目前尝试过的方法，

import numpy as np
import json
from sklearn.naive_bayes import *

topic = []
question = []
excerpt = []

with open('training.json') as f:
    for line in f:
        data = json.loads(line)
        topic.append(data["topic"])
        question.append(data["question"])
        excerpt.append(data["excerpt"])

unique_topics = list(set(topic))
new_topic = [x.encode('UTF8') for x in topic]
numeric_topics = [name.replace('gis', '1').replace('security', '2').replace('photo', '3').replace('mathematica', '4').replace('unix', '5').replace('wordpress', '6').replace('scifi', '7').replace('electronics', '8').replace('android', '9').replace('apple', '10') for name in new_topic]
numeric_topics = [float(i) for i in numeric_topics]

x1 = np.array(question)
x2 = np.array(excerpt)
X = zip(*[x1,x2])
Y = np.array(numeric_topics)
print X[0]
clf = BernoulliNB()
clf.fit(X, Y)
print "Prediction:", clf.predict( ['hello'] )

但正如预期的那样，我收到 ValueError: 无法将字符串转换为浮点数。我的问题是如何创建一个简单的分类器来将问题和摘录分类为相关主题？

Answer 1

sklearn 中的所有分类器都需要将输入表示为某个固定维度的向量。对于文本，有 CountVectorizer, HashingVectorizer and TfidfVectorizer 可以将您的字符串转换为浮点数向量。

vect = TfidfVectorizer()
X = vect.fit_transform(X)

显然，您需要以相同的方式向量化您的测试集

clf.predict( vect.transform(['hello']) )

看到一个tutorial on using sklearn with textual data。

如何使用 sklearn 库对朴素贝叶斯进行文本分类？

How to perform text classification with naive bayes using sklearn library?

python

machine-learning

scikit-learn

text-classification

naivebayes