Python plotTree.py —— 决策树绘图模块函数

 Python plotTree.py —— 决策树绘图模块函数

保存以下代码为plotTree.py，在所需调用的py文件，加入代码：

import plotTree


plotTree.createPlot(Tree)

plotTree.py ：

import matplotlib.pyplot as plt
from pylab import *

# 定义文本框和箭头格式
decisionNode = dict(boxstyle="sawtooth", fc="0.8")
leafNode = dict(boxstyle="round4", fc="0.8")
arrow_args = dict(arrowstyle="<-")
mpl.rcParams['font.sans-serif'] = ['SimHei'] #指定默认字体
mpl.rcParams['axes.unicode_minus'] = False #解决保存图像是负号'-'显示为方块的问题

def plotMidText(cntrPt, parentPt, txtString):
	xMid = (parentPt[0]-cntrPt[0])/2.0 + cntrPt[0]
	yMid = (parentPt[1]-cntrPt[1])/2.0 + cntrPt[1]
	createPlot.ax1.text(xMid, yMid, txtString)

def plotNode(nodeTxt, centerPt, parentPt, nodeType): # 绘制带箭头的注解
    createPlot.ax1.annotate(nodeTxt, xy=parentPt, xycoords="axes fraction", xytext=centerPt, textcoords="axes fraction", va="center", ha="center", bbox=nodeType, arrowprops=arrow_args)

def getNumLeafs(myTree): # 获取叶节点的数目
    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

def getTreeDepth(myTree): # 获取树的层数
    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

def retrieveTree(i): # 获取预定义的树
    listOfTrees =[{'no surfacing': {0: 'no', 1: {'flippers': {0: 'no', 1: 'yes'}}}},
                  {'no surfacing': {0: 'no', 1: {'flippers': {0: {'head': {0: 'no', 1: 'yes'}}, 1: 'no'}}}}
                  ]
    return listOfTrees[i]

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

def createPlot(inTree):
	fig = plt.figure(1, figsize=(600, 30), 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.xOff = -0.5/plotTree.totalW; plotTree.yOff = 1.0;
	plotTree(inTree, (0.5,1.0), '')
	plt.show()