Python_sklearn机器学习库学习笔记(四)decision_tree(决策树)
2024-08-25 08:44:49
# 决策树
import pandas as pd
from sklearn.tree import DecisionTreeClassifier
from sklearn.cross_validation import train_test_split
from sklearn.metrics import classification_report
from sklearn.pipeline import Pipeline
from sklearn.grid_search import GridSearchCV
import zipfile
#压缩节省空间
z=zipfile.ZipFile('ad-dataset.zip')
# df=pd.read_csv(z.open(z.namelist()[0]),header=None,low_memory=False)
# df = pd.read_csv(z.open(z.namelist()[0]), header=None, low_memory=False)
df=pd.read_csv('.\\tree_data\\ad.data',header=None)
explanatory_variable_columns=set(df.columns.values)
response_variable_column=df[len(df.columns.values)-1]
#最后一列是代表的标签类型
explanatory_variable_columns.remove(len(df.columns)-1)
y=[1 if e =='ad.' else 0 for e in response_variable_column]
X=df.loc[:,list(explanatory_variable_columns)]
#匹配?字符,并把值转化为-1
X.replace(to_replace=' *\?', value=-1, regex=True, inplace=True)
X_train,X_test,y_train,y_test=train_test_split(X,y)
#用信息增益启发式算法建立决策树
pipeline=Pipeline([('clf',DecisionTreeClassifier(criterion='entropy'))])
parameters = {
'clf__max_depth': (150, 155, 160),
'clf__min_samples_split': (1, 2, 3),
'clf__min_samples_leaf': (1, 2, 3)
}
#f1查全率和查准率的调和平均
grid_search=GridSearchCV(pipeline,parameters,n_jobs=-1,
verbose=1,scoring='f1')
grid_search.fit(X_train,y_train)
print '最佳效果:%0.3f'%grid_search.best_score_
print '最优参数'
best_parameters=grid_search.best_estimator_.get_params()
best_parameters
输出结果:
Fitting 3 folds for each of 27 candidates, totalling 81 fits
[Parallel(n_jobs=-1)]: Done 46 tasks | elapsed: 21.0s
[Parallel(n_jobs=-1)]: Done 81 out of 81 | elapsed: 34.7s finished
最佳效果:0.888
最优参数
Out[123]:
{'clf': DecisionTreeClassifier(class_weight=None, criterion='entropy', max_depth=160,
max_features=None, max_leaf_nodes=None, min_samples_leaf=1,
min_samples_split=3, min_weight_fraction_leaf=0.0,
presort=False, random_state=None, splitter='best'),
'clf__class_weight': None,
'clf__criterion': 'entropy',
'clf__max_depth': 160,
'clf__max_features': None,
'clf__max_leaf_nodes': None,
'clf__min_samples_leaf': 1,
'clf__min_samples_split': 3,
'clf__min_weight_fraction_leaf': 0.0,
'clf__presort': False,
'clf__random_state': None,
'clf__splitter': 'best',
'steps': [('clf',
DecisionTreeClassifier(class_weight=None, criterion='entropy', max_depth=160,
max_features=None, max_leaf_nodes=None, min_samples_leaf=1,
min_samples_split=3, min_weight_fraction_leaf=0.0,
presort=False, random_state=None, splitter='best'))]}
for param_name in sorted(parameters.keys()):
print ('\t%s:%r'%(param_name,best_parameters[param_name]))
predictions=grid_search.predict(X_test)
print classification_report(y_test,predictions)
输出结果:
clf__max_depth:150
clf__min_samples_leaf:1
clf__min_samples_split:1
precision recall f1-score support
0 0.97 0.99 0.98 703
1 0.91 0.84 0.87 117
avg / total 0.96 0.96 0.96 820
df.head()
输出结果;
0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | ... | 1549 | 1550 | 1551 | 1552 | 1553 | 1554 | 1555 | 1556 | 1557 | 1558 | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0 | 125 | 125 | 1.0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ad. |
1 | 57 | 468 | 8.2105 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ad. |
2 | 33 | 230 | 6.9696 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ad. |
3 | 60 | 468 | 7.8 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ad. |
4 | 60 | 468 | 7.8 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ad. |
# 决策树集成
#coding:utf-8
import pandas as pd
from sklearn.ensemble import RandomForestClassifier
from sklearn.cross_validation import train_test_split
from sklearn.metrics import classification_report
from sklearn.pipeline import Pipeline
from sklearn.grid_search import GridSearchCV df=pd.read_csv('.\\tree_data\\ad.data',header=None,low_memory=False)
explanatory_variable_columns=set(df.columns.values)
response_variable_column=df[len(df.columns.values)-1]
df.head()
0 | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | ... | 1549 | 1550 | 1551 | 1552 | 1553 | 1554 | 1555 | 1556 | 1557 | 1558 | |
---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
0 | 125 | 125 | 1.0 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ad. |
1 | 57 | 468 | 8.2105 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ad. |
2 | 33 | 230 | 6.9696 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ad. |
3 | 60 | 468 | 7.8 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ad. |
4 | 60 | 468 | 7.8 | 1 | 0 | 0 | 0 | 0 | 0 | 0 | ... | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | ad. |
#The last column describes the targets(去掉最后一列)
explanatory_variable_columns.remove(len(df.columns.values)-1)
y=[1 if e=='ad.' else 0 for e in response_variable_column]
X=df.loc[:,list(explanatory_variable_columns)]
#置换有?的为-1
X.replace(to_replace=' *\?', value=-1, regex=True, inplace=True)
X_train,X_test,y_train,y_test=train_test_split(X,y)
pipeline=Pipeline([('clf',RandomForestClassifier(criterion='entropy'))])
parameters = {
'clf__n_estimators': (5, 10, 20, 50),
'clf__max_depth': (50, 150, 250),
'clf__min_samples_split': (1, 2, 3),
'clf__min_samples_leaf': (1, 2, 3)
}
grid_search = GridSearchCV(pipeline,parameters,n_jobs=-1,verbose=1,scoring='f1')
grid_search.fit(X_train,y_train)
print(u'最佳效果:%0.3f'%grid_search.best_score_)
print u'最优的参数:'
best_parameters=grid_search.best_estimator_.get_params()
for param_name in sorted(parameters.keys()):
print('\t%s:%r'%(param_name,best_parameters[param_name]))
输出结果:
最佳效果:0.929 最优的参数: clf__max_depth:250 clf__min_samples_leaf:1 clf__min_samples_split:3 clf__n_estimators:50
predictions=grid_search.predict(X_test)
print classification_report(y_test,predictions)
输出结果:
precision recall f1-score support
0 0.98 1.00 0.99 705
1 0.97 0.90 0.93 115
avg / total 0.98 0.98 0.98 820
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