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前些天对决策树算法有了一个基本的了解,下面就这一个算法做实际应用的记录:
一、Python机器学习库:scikit-learn
1.1 特性:
- 简单高效的数据挖掘和机器学习分析
- 对所有用户开放,根据不同需求高度可重用性
- 基于Numpy,SciPy和matplotlib包
- 开源,商用级别:获得BSD许可
1.2 覆盖的问题领域:
- 分类(classification)
- 回归(regression)
- 聚类(clustering)
- 降维(dimensionnality reduction)
- 模型选择(model selection)
- 预处理(preprocessing)
1.3 安装和使用scikit-learn
安装方式:
- pip/pip3
- easy_install
- windows installar
安装包:
- numpy
- SciPy
- matplotlib
- 可使用Anaconda(包含numpy,scipy等科学计算常用的包)
相关引用:
from sklearn.feature_extraction import DictVectorizer
import csv
from sklearn import preprocessing
from sklearn import tree
from sklearn.externals.six import StringIO
1.4 例子
这是一个购买电脑的数据集,我们把这些数据创建在excel表中方便python进行数据的读取,于是创建一个“decision_tree.csv”将数据输入进去。
from sklearn.feature_extraction import DictVectorizer
import csv
from sklearn import tree
from sklearn import preprocessing
from sklearn.externals.six import StringIO
# Read in the csv file and put features into list of dict and list of class label
allElectronicsData = open(r'/home/zhoumiao/MachineLearning/01decisiontree/AllElectronics.csv', 'rb')
reader = csv.reader(allElectronicsData)
headers = reader.next()
print(headers)
featureList = []
labelList = []
for row in reader:
labelList.append(row[len(row)-1])
rowDict = {}
for i in range(1, len(row)-1):
rowDict[headers[i]] = row[i]
featureList.append(rowDict)
print(featureList)
# Vetorize features
vec = DictVectorizer()
dummyX = vec.fit_transform(featureList) .toarray()
print("dummyX: " + str(dummyX))
print(vec.get_feature_names())
print("labelList: " + str(labelList))
# vectorize class labels
lb = preprocessing.LabelBinarizer()
dummyY = lb.fit_transform(labelList)
print("dummyY: " + str(dummyY))
# Using decision tree for classification
# clf = tree.DecisionTreeClassifier()
clf = tree.DecisionTreeClassifier(criterion='entropy')
clf = clf.fit(dummyX, dummyY)
print("clf: " + str(clf))
# Visualize model
with open("allElectronicInformationGainOri.dot", 'w') as f:
f = tree.export_graphviz(clf, feature_names=vec.get_feature_names(), out_file=f)
oneRowX = dummyX[0, :]
print("oneRowX: " + str(oneRowX))
newRowX = oneRowX
newRowX[0] = 1
newRowX[2] = 0
print("newRowX: " + str(newRowX))
predictedY = clf.predict(newRowX)
print("predictedY: " + str(predictedY))