使用Scikit-learn计算信息增益 [英] Information Gain calculation with Scikit-learn
问题描述
我使用Scikit学习的文本分类.我要计算的信息增益用于在(稀疏)文档术语矩阵相对于每个属性的一类. 信息增益被定义为H(类) - H(类|属性),其中H是熵.
I am using Scikit-learn for text classification. I want to calculate the Information Gain for each attribute with respect to a class in a (sparse) document-term matrix. The Information Gain is defined as H(Class) - H(Class | Attribute), where H is the entropy.
使用weka可以通过 InfoGainAttribute实现.但是我还没有发现这一措施在scikit学习.
Using weka, this can be accomplished with the InfoGainAttribute. But I haven't found this measure in scikit-learn.
然而,它已经建议该公式对于以上信息增益是相同的措施,因为互信息.此比赛也维基中的定义.
However, it has been suggested that the formula above for Information Gain is the same measure as mutual information. This matches also the definition in wikipedia.
是否可以使用特定的设置相互信息scikit学习来完成这个任务?
Is it possible to use a specific setting for mutual information in scikit-learn to accomplish this task?
推荐答案
You can use scikit-learn's mutual_info_classif
here is an example
from sklearn.datasets import fetch_20newsgroups
from sklearn.feature_selection import mutual_info_classif
from sklearn.feature_extraction.text import CountVectorizer
categories = ['talk.religion.misc',
'comp.graphics', 'sci.space']
newsgroups_train = fetch_20newsgroups(subset='train',
categories=categories)
X, Y = newsgroups_train.data, newsgroups_train.target
cv = CountVectorizer(max_df=0.95, min_df=2,
max_features=10000,
stop_words='english')
X_vec = cv.fit_transform(X)
res = dict(zip(cv.get_feature_names(),
mutual_info_classif(X_vec, Y, discrete_features=True)
))
print(res)
此将输出每个属性的词典,即在词汇作为键项目和它们的增益信息作为值
this will output a dictionary of each attribute, i.e. item in the vocabulary as keys and their information gain as values
这里是输出
{'bible': 0.072327479595571439,
'christ': 0.057293733680219089,
'christian': 0.12862867565281702,
'christians': 0.068511328611810071,
'file': 0.048056478042481157,
'god': 0.12252523919766867,
'gov': 0.053547274485785577,
'graphics': 0.13044709565039875,
'jesus': 0.09245436105573257,
'launch': 0.059882179387444862,
'moon': 0.064977781072557236,
'morality': 0.050235104394123153,
'nasa': 0.11146392824624819,
'orbit': 0.087254803670582998,
'people': 0.068118370234354936,
'prb': 0.049176995204404481,
'religion': 0.067695617096125316,
'shuttle': 0.053440976618359261,
'space': 0.20115901737978983,
'thanks': 0.060202010019767334}
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