https://classroom.udacity.com/nanodegrees/nd009/parts/0091345404/modules/6a945ec8-573e-4a60-8d6b-a0fed6abed44/lessons/5450810003/concepts/24402485560923
邦族文档
帮助文档http://scikit-learn.org/stable/modules/generated/sklearn.tree.DecisionTreeClassifier.html
此处求得不是熵,是概率
import scipy.stats
print scipy.stats.entropy([2,1],base=2)
原文:http://www.cnblogs.com/bettyty/p/6250086.html