sklearn 的 Decision Trees
sklearn.tree的函数结构：
1、介绍：
are a non-parametric supervised learning method used for classification and regression. The goal is to create a model that predicts the value of a target variable by learning simple decision rules inferred from the data features.
（无参，可得到类别，也可得到一连续的回归结果）
2、Classification
函数：DecisionTreeClassifer
Alternatively, the probability of each class can be predicted, which is the fraction of training samples of the same class in a leaf:(可以预测每个类的概率，即同一类训练样本在叶片中的比例):
可将树进行可视化：
3、Regression