Scikit-Learn 决策树：预测概率是 a 还是 b？

Question

我有一个带有 Scikit-Learn 的基本决策树分类器：

#Used to determine men from women based on height and shoe size

from sklearn import tree

#height and shoe size
X = [[65,9],[67,7],[70,11],[62,6],[60,7],[72,13],[66,10],[67,7.5]]

Y=["male","female","male","female","female","male","male","female"]

#creating a decision tree
clf = tree.DecisionTreeClassifier()

#fitting the data to the tree
clf.fit(X, Y)

#predicting the gender based on a prediction
prediction = clf.predict([68,9])

#print the predicted gender
print(prediction)

当我运行程序时，它总是输出“男性”或“女性”，但是我如何才能看到预测是男性还是女性的概率？例如，上面的预测返回“男性”，但我如何让它打印预测为男性的概率？

谢谢！

Answer 1

您可以执行以下操作：

from sklearn import tree

#load data
X = [[65,9],[67,7],[70,11],[62,6],[60,7],[72,13],[66,10],[67,7.5]]
Y=["male","female","male","female","female","male","male","female"]

#build model
clf = tree.DecisionTreeClassifier()

#fit
clf.fit(X, Y)

#predict
prediction = clf.predict([[68,9],[66,9]])

#probabilities
probs = clf.predict_proba([[68,9],[66,9]])

#print the predicted gender
print(prediction)
print(probs)

理论

结果clf.predict_proba(X)是： 预测的类概率，即叶子中同一类样本的比例。

结果解读：

第一个print返回，['male' 'male']因此数据[[68,9],[66,9]]预测为males。

第二个print返回：

[[ 0. 1.] [ 0. 1.]]

这意味着数据被预测为男性，这是由第二列中的数据报告的。

要查看类的顺序，请使用：clf.classes_

这将返回：['female', 'male']