如何實現(xiàn)Python3 ID3決策樹判斷申請貸款是否成功

# -*- coding: utf-8 -*-
#生成樹的函數(shù)

from numpy import * 
import numpy as np
import pandas as pd
from math import log 
import operator 

# 計算數(shù)據(jù)集的信息熵(Information Gain)增益函數(shù)(機器學習實戰(zhàn)中信息熵叫香農(nóng)熵)
def calcInfoEnt(dataSet):#本題中Label即好or壞瓜 #dataSet每一列是一個屬性(列末是Label)
 numEntries = len(dataSet) #每一行是一個樣本
 labelCounts = {} #給所有可能的分類創(chuàng)建字典labelCounts
 for featVec in dataSet: #按行循環(huán)：即rowVev取遍了數(shù)據(jù)集中的每一行
  currentLabel = featVec[-1] #故featVec[-1]取遍每行最后一個值即Label
  if currentLabel not in labelCounts.keys(): #如果當前的Label在字典中還沒有
   labelCounts[currentLabel] = 0 #則先賦值0來創(chuàng)建這個詞
  labelCounts[currentLabel] += 1 #計數(shù), 統(tǒng)計每類Label數(shù)量(這行不受if限制)
 InfoEnt = 0.0
 for key in labelCounts: #遍歷每類Label
  prob = float(labelCounts[key])/numEntries #各類Label熵累加
  InfoEnt -= prob * log(prob,2) #ID3用的信息熵增益公式
 return InfoEnt

### 對于離散特征: 取出該特征取值為value的所有樣本
def splitDiscreteDataSet(dataSet, axis, value): #dataSet是當前結(jié)點(待劃分)集合,axis指示劃分所依據(jù)的屬性,value該屬性用于劃分的取值
 retDataSet = []  #為return Data Set分配一個列表用來儲存
 for featVec in dataSet:
  if featVec[axis] == value:
   reducedFeatVec = featVec[:axis]   #該特征之前的特征仍保留在樣本dataSet中
   reducedFeatVec.extend(featVec[axis+1:]) #該特征之后的特征仍保留在樣本dataSet中
   retDataSet.append(reducedFeatVec)  #把這個樣本加到list中
 return retDataSet

### 對于連續(xù)特征: 返回特征取值大于value的所有樣本(以value為閾值將集合分成兩部分)
def splitContinuousDataSet(dataSet, axis, value): 
 retDataSetG = []  #將儲存取值大于value的樣本
 retDataSetL = []  #將儲存取值小于value的樣本 
 for featVec in dataSet: 
  if featVec[axis] > value: 
   reducedFeatVecG = featVec[:axis]
   reducedFeatVecG.extend(featVec[axis+1:]) 
   retDataSetG.append(reducedFeatVecG)
  else:
   reducedFeatVecL = featVec[:axis]
   reducedFeatVecL.extend(featVec[axis+1:]) 
   retDataSetL.append(reducedFeatVecL)
 return retDataSetG,retDataSetL  #返回兩個集合, 是含2個元素的tuple形式

### 根據(jù)InfoGain選擇當前最好的劃分特征(以及對于連續(xù)變量還要選擇以什么值劃分)
def chooseBestFeatureToSplit(dataSet,labels): 
 numFeatures = len(dataSet[0])-1
 baseEntropy = calcInfoEnt(dataSet) 
 bestInfoGain = 0.0; bestFeature = -1
 bestSplitDict = {}
 for i in range(numFeatures):
  #遍歷所有特征：下面這句是取每一行的第i個, 即得當前集合所有樣本第i個feature的值
  featList = [example[i] for example in dataSet]
  #判斷是否為離散特征
  if not (type(featList[0]).__name__=='float' or type(featList[0]).__name__=='int'): 
# 對于離散特征：求若以該特征劃分的熵增
   uniqueVals = set(featList)  #從列表中創(chuàng)建集合set(得列表唯一元素值)
   newEntropy = 0.0
   for value in uniqueVals:  #遍歷該離散特征每個取值
    subDataSet = splitDiscreteDataSet(dataSet, i, value)#計算每個取值的信息熵
    prob = len(subDataSet)/float(len(dataSet))
    newEntropy += prob * calcInfoEnt(subDataSet)#各取值的熵累加
   infoGain = baseEntropy - newEntropy #得到以該特征劃分的熵增 
# 對于連續(xù)特征：求若以該特征劃分的熵增(區(qū)別：n個數(shù)據(jù)則需添n-1個候選劃分點, 并選最佳劃分點) 
  else: #產(chǎn)生n-1個候選劃分點 
   sortfeatList=sorted(featList) 
   splitList=[] 
   for j in range(len(sortfeatList)-1): #產(chǎn)生n-1個候選劃分點
    splitList.append((sortfeatList[j] + sortfeatList[j+1])/2.0) 
   bestSplitEntropy = 10000     #設(shè)定一個很大的熵值(之后用)
   #遍歷n-1個候選劃分點: 求選第j個候選劃分點劃分時的熵增, 并選出最佳劃分點
   for j in range(len(splitList)):
    value = splitList[j] 
    newEntropy = 0.0 
    DataSet = splitContinuousDataSet(dataSet, i, value)
    subDataSetG = DataSet[0]
    subDataSetL = DataSet[1] 
    probG = len(subDataSetG) / float(len(dataSet)) 
    newEntropy += probG * calcInfoEnt(subDataSetG) 
    probL = len(subDataSetL) / float(len(dataSet)) 
    newEntropy += probL * calcInfoEnt(subDataSetL)
    if newEntropy < bestSplitEntropy: 
     bestSplitEntropy = newEntropy
     bestSplit = j
   bestSplitDict[labels[i]] = splitList[bestSplit]#字典記錄當前連續(xù)屬性的最佳劃分點
   infoGain = baseEntropy - bestSplitEntropy  #計算以該節(jié)點劃分的熵增
# 在所有屬性(包括連續(xù)和離散)中選擇可以獲得最大熵增的屬性
  if infoGain > bestInfoGain: 
   bestInfoGain = infoGain
   bestFeature = i
 #若當前節(jié)點的最佳劃分特征為連續(xù)特征，則需根據(jù)“是否小于等于其最佳劃分點”進行二值化處理
 #即將該特征改為“是否小于等于bestSplitValue”, 例如將“密度”變?yōu)椤懊芏?lt;=0.3815”
 #注意：以下這段直接操作了原dataSet數(shù)據(jù), 之前的那些float型的值相應(yīng)變?yōu)?和1
 #【為何這樣做&#63;】在函數(shù)createTree()末尾將看到解釋
 if type(dataSet[0][bestFeature]).__name__=='float' or type(dataSet[0][bestFeature]).__name__=='int':  
  bestSplitValue = bestSplitDict[labels[bestFeature]] 
  labels[bestFeature] = labels[bestFeature] + '<=' + str(bestSplitValue)
  for i in range(shape(dataSet)[0]): 
   if dataSet[i][bestFeature] <= bestSplitValue: 
    dataSet[i][bestFeature] = 1 
   else: 
    dataSet[i][bestFeature] = 0
 return bestFeature  

# 若特征已經(jīng)劃分完，節(jié)點下的樣本還沒有統(tǒng)一取值，則需要進行投票：計算每類Label個數(shù), 取max者
def majorityCnt(classList): 
 classCount = {}  #將創(chuàng)建鍵值為Label類型的字典
 for vote in classList: 
  if vote not in classCount.keys(): 
   classCount[vote] = 0  #第一次出現(xiàn)的Label加入字典
  classCount[vote] += 1  #計數(shù)
 return max(classCount)

# 主程序：遞歸產(chǎn)生決策樹
 # dataSet：當前用于構(gòu)建樹的數(shù)據(jù)集, 最開始就是data_full，然后隨著劃分的進行越來越小。這是因為進行到到樹分叉點上了. 第一次劃分之前17個瓜的數(shù)據(jù)在根節(jié)點，然后選擇第一個bestFeat是紋理. 紋理的取值有清晰、模糊、稍糊三種；將瓜分成了清晰（9個），稍糊（5個），模糊（3個）,這時應(yīng)該將劃分的類別減少1以便于下次劃分。 
 # labels：當前數(shù)據(jù)集中有的用于劃分的類別(這是因為有些Label當前數(shù)據(jù)集沒了, 比如假如到某個點上西瓜都是淺白沒有深綠了)
 # data_full：全部的數(shù)據(jù) 
 # label_full:全部的類別 

numLine = numColumn = 2 #這句是因為之后要用global numLine……至于為什么我一定要用global

# 我也不完全理解。如果我只定義local變量總報錯，我只好在那里的if里用global變量了。求解。

def createTree(dataSet,labels,data_full,labels_full): 
 classList = [example[-1] for example in dataSet] 
 #遞歸停止條件1：當前節(jié)點所有樣本屬于同一類；(注：count()方法統(tǒng)計某元素在列表中出現(xiàn)的次數(shù))
 if classList.count(classList[0]) == len(classList): 
  return classList[0]
 
#遞歸停止條件2：當前節(jié)點上樣本集合為空集(即特征的某個取值上已經(jīng)沒有樣本了)：
 global numLine,numColumn
 (numLine,numColumn) = shape(dataSet)
 if float(numLine) == 0: 
  return 'empty'
 
#遞歸停止條件3：所有可用于劃分的特征均使用過了，則調(diào)用majorityCnt()投票定Label；
 if float(numColumn) == 1: 
  return majorityCnt(classList) 
 
#不停止時繼續(xù)劃分：
 bestFeat = chooseBestFeatureToSplit(dataSet,labels)#調(diào)用函數(shù)找出當前最佳劃分特征是第幾個
 bestFeatLabel = labels[bestFeat]  #當前最佳劃分特征
 myTree = {bestFeatLabel:{}} 
 featValues = [example[bestFeat] for example in dataSet] 
 uniqueVals = set(featValues) 
 if type(dataSet[0][bestFeat]).__name__=='str': 
  currentlabel = labels_full.index(labels[bestFeat]) 
  featValuesFull = [example[currentlabel] for example in data_full] 
  uniqueValsFull = set(featValuesFull) 
 del(labels[bestFeat]) #劃分完后, 即當前特征已經(jīng)使用過了, 故將其從“待劃分特征集”中刪去

 #【遞歸調(diào)用】針對當前用于劃分的特征(beatFeat)的每個取值，劃分出一個子樹。 
 for value in uniqueVals: #遍歷該特征【現(xiàn)存的】取值
  subLabels = labels[:] 
  if type(dataSet[0][bestFeat]).__name__=='str': 
   uniqueValsFull.remove(value)  #劃分后刪去(從uniqueValsFull中刪!)
  myTree[bestFeatLabel][value] = createTree(splitDiscreteDataSet(dataSet,bestFeat,value),subLabels,data_full,labels_full)#用splitDiscreteDataSet()
 #是由于, 所有的連續(xù)特征在劃分后都被我們定義的chooseBestFeatureToSplit()處理成離散取值了。
 if type(dataSet[0][bestFeat]).__name__=='str': #若該特征離散【更詳見后注】
  for value in uniqueValsFull:#則可能有些取值已經(jīng)不在【現(xiàn)存的】取值中了
 #這就是上面為何從“uniqueValsFull”中刪去
 #因為那些現(xiàn)有數(shù)據(jù)集中沒取到的該特征的值，保留在了其中
   myTree[bestFeatLabel][value] = majorityCnt(classList) 

 return myTree 

#生成樹調(diào)用的語句
df = pd.read_excel(r'E:\BaiduNetdiskDownload\spss\數(shù)據(jù)\實驗data\銀行貸款.xlsx') 
data = df.values[:,1:].tolist() 
data_full = data[:] 
labels = df.columns.values[1:-1].tolist() 
labels_full = labels[:] 
myTree = createTree(data,labels,data_full,labels_full) 

#繪決策樹的函數(shù)
import matplotlib.pyplot as plt 
decisionNode = dict(boxstyle = "sawtooth",fc = "0.8") #定義分支點的樣式
leafNode = dict(boxstyle = "round4",fc = "0.8") #定義葉節(jié)點的樣式
arrow_args = dict(arrowstyle = "<-") #定義箭頭標識樣式

# 計算樹的葉子節(jié)點數(shù)量 
def getNumLeafs(myTree):
 numLeafs = 0 
 firstStr = list(myTree.keys())[0]
 secondDict = myTree[firstStr]
 for key in secondDict.keys(): 
  if type(secondDict[key]).__name__=='dict': 
   numLeafs += getNumLeafs(secondDict[key]) 
  else: numLeafs += 1
 return numLeafs

# 計算樹的最大深度
def getTreeDepth(myTree): 
 maxDepth = 0 
 firstStr = list(myTree.keys())[0] 
 secondDict = myTree[firstStr] 
 for key in secondDict.keys(): 
  if type(secondDict[key]).__name__=='dict': 
   thisDepth = 1 + getTreeDepth(secondDict[key]) 
  else: thisDepth = 1 
  if thisDepth > maxDepth: 
   maxDepth = thisDepth
 return maxDepth 

# 畫出節(jié)點 
def plotNode(nodeTxt,centerPt,parentPt,nodeType): 
 createPlot.ax1.annotate(nodeTxt,xy = parentPt,xycoords = 'axes fraction',xytext = centerPt,textcoords = 'axes fraction',va = "center", ha = "center",bbox = nodeType,arrowprops = arrow_args) 

# 標箭頭上的文字 
def plotMidText(cntrPt,parentPt,txtString): 
 lens = len(txtString) 
 xMid = (parentPt[0] + cntrPt[0]) / 2.0 - lens*0.002 
 yMid = (parentPt[1] + cntrPt[1]) / 2.0 
 createPlot.ax1.text(xMid,yMid,txtString) 

def plotTree(myTree,parentPt,nodeTxt): 
 numLeafs = getNumLeafs(myTree) 
 depth = getTreeDepth(myTree) 
 firstStr = list(myTree.keys())[0] 
 cntrPt = (plotTree.x0ff + (1.0 + float(numLeafs))/2.0/plotTree.totalW,plotTree.y0ff) 
 plotMidText(cntrPt,parentPt,nodeTxt) 
 plotNode(firstStr,cntrPt,parentPt,decisionNode) 
 secondDict = myTree[firstStr] 
 plotTree.y0ff = plotTree.y0ff - 1.0/plotTree.totalD 
 for key in secondDict.keys(): 
  if type(secondDict[key]).__name__=='dict': 
   plotTree(secondDict[key],cntrPt,str(key)) 
  else: 
   plotTree.x0ff = plotTree.x0ff + 1.0/plotTree.totalW 
   plotNode(secondDict[key],(plotTree.x0ff,plotTree.y0ff),cntrPt,leafNode) 
   plotMidText((plotTree.x0ff,plotTree.y0ff),cntrPt,str(key)) 
 plotTree.y0ff = plotTree.y0ff + 1.0/plotTree.totalD 

def createPlot(inTree): 
 fig = plt.figure(1,facecolor = 'white') 
 fig.clf() 
 axprops = dict(xticks = [],yticks = []) 
 createPlot.ax1 = plt.subplot(111,frameon = False,**axprops) 
 plotTree.totalW = float(getNumLeafs(inTree)) 
 plotTree.totalD = float(getTreeDepth(inTree)) 
 plotTree.x0ff = -0.5/plotTree.totalW 
 plotTree.y0ff = 1.0 
 plotTree(inTree,(0.5,1.0),'') 
 plt.show()

#命令繪決策樹的圖
createPlot(myTree)