scikit-learn机器学习(四)使用决策树做分类,并画出决策树,随机森林对比

数据来自 UCI 数据集 匹马印第安人糖尿病数据集

载入数据

# -*- coding: utf-8 -*-
import pandas as pd
import matplotlib
matplotlib.rcParams['font.sans-serif']=[u'simHei']
matplotlib.rcParams['axes.unicode_minus']=False
from sklearn.tree import DecisionTreeClassifier
from sklearn.model_selection import train_test_split
from sklearn.metrics import classification_report
from sklearn.pipeline import Pipeline
from sklearn.model_selection import GridSearchCV
 
from sklearn.datasets import load_breast_cancer
 
data_set = pd.read_csv('pima-indians-diabetes.csv')
data = data_set.values[:,:]
 
y = data[:,8]
X = data[:,:8]
X_train,X_test,y_train,y_test = train_test_split(X,y)

建立决策树，网格搜索微调模型

# In[1] 网格搜索微调模型
pipeline = Pipeline([
        ('clf',DecisionTreeClassifier(criterion='entropy'))
        ])
parameters={
        'clf__max_depth':(3,5,10,15,20,25,30,35,40),
        'clf__min_samples_split':(2,3),
        'clf__min_samples_leaf':(1,2,3)
        }
#GridSearchCV 用于系统地遍历多种参数组合，通过交叉验证确定最佳效果参数。
grid_search = GridSearchCV(pipeline,parameters,n_jobs=-1,verbose=-1,scoring='f1')
grid_search.fit(X_train,y_train)
 
# 获取搜索到的最优参数
best_parameters = grid_search.best_estimator_.get_params()
print("最好的F1值为：",grid_search.best_score_)
print('最好的参数为：')
for param_name in sorted(parameters.keys()):
    print('t%s: %r' % (param_name,best_parameters[param_name]))
 
# In[2] 输出预测结果并评价
predictions = grid_search.predict(X_test)
print(classification_report(y_test,predictions))

最好的F1值为： 0.5573515325670498
最好的参数为：
tclf__max_depth: 5
tclf__min_samples_leaf: 1
tclf__min_samples_split: 2

评价模型

# In[2] 输出预测结果并评价
predictions = grid_search.predict(X_test)
print(classification_report(y_test,predictions))

              precision    recall  f1-score   support
 
         0.0       0.74      0.89      0.81       124
         1.0       0.67      0.43      0.52        68

画出决策树

# In[3]打印树
from sklearn import tree
feature_name=data_set.columns.values.tolist()[:-1]   # 列名称
DT = tree.DecisionTreeClassifier(criterion='entropy',max_depth=5,min_samples_split=2,min_samples_leaf=5)
DT.fit(X_train,y_train)
 
'''
# 法一
import pydotplus
from sklearn.externals.six import StringIO
dot_data = StringIO()
tree.export_graphviz(DT,out_file = dot_data,feature_names=feature_name,
                     class_names=["有糖尿病","无病"],filled=True,rounded=True,
                     special_characters=True)
graph = pydotplus.graph_from_dot_data(dot_data.getvalue())
graph.write_pdf("Tree.pdf")
print('Visible tree plot saved as pdf.')
'''
 
# 法二
import graphviz
#ID3为决策树分类器fit之后得到的模型，注意这里必须在fit后执行，在predict之后运行会报错
dot_data = tree.export_graphviz(DT, out_file=None,feature_names=feature_name,class_names=["有糖尿病","无病"]) # doctest: +SKIP
graph = graphviz.Source(dot_data) # doctest: +SKIP
#在同级目录下生成tree.pdf文件
graph.render("tree2") # doctest: +SKIP

随机森林

# -*- coding: utf-8 -*-
import pandas as pd
import matplotlib
matplotlib.rcParams['font.sans-serif']=[u'simHei']
matplotlib.rcParams['axes.unicode_minus']=False
from sklearn.tree import DecisionTreeClassifier
from sklearn.model_selection import train_test_split
from sklearn.metrics import classification_report
from sklearn.pipeline import Pipeline
from sklearn.model_selection import GridSearchCV
from sklearn.ensemble import RandomForestClassifier
 
from sklearn.datasets import load_breast_cancer
 
data_set = pd.read_csv('pima-indians-diabetes.csv')
data = data_set.values[:,:]
 
y = data[:,8]
X = data[:,:8]
X_train,X_test,y_train,y_test = train_test_split(X,y)
 
RF = RandomForestClassifier(n_estimators=10,random_state=11)
RF.fit(X_train,y_train)
predictions = RF.predict(X_test)
print(classification_report(y_test,predictions))

              precision    recall  f1-score   support
 
         0.0       0.82      0.91      0.86       126
         1.0       0.78      0.61      0.68        66
 
   micro avg       0.81      0.81      0.81       192
   macro avg       0.80      0.76      0.77       192
weighted avg       0.80      0.81      0.80       192