python ?W?j?? pythonw决策树回归绘制图

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lazihuman 2023-06-21 00:21:02

文章标签 python ?W?j?? python 绘图结点决策树 文章分类 Python 后端开发

在绘图中要用到matplotlib这个库文件。

其中里面要用到的subplot(),annotate(),

subplot(nrows, ncols, plot_number) #表示行列以及当前的是第几个图形，frameon表示是否有边框

画出带箭头的注释：

annotate(s, xy, xytext=None, xycoords='data',textcoords='data', arrowprops=None, **kwargs)

绘图如下：

决策树绘图的代码：

import matplotlib.pyplot as plt

#定义文本框和箭头格式
decisionNode = dict(boxstyle="sawtooth",fc='0.8')#定义判断结点形态
leafNode = dict(boxstyle="round4",fc="0.8")#定义叶结点形态
arrow_args = dict(arrowstyle="<-")#定义箭头

#绘制带箭头的注释
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)
#计算叶结点数
def getNumLeafs(myTree):
    numLeafs = 0
    firstStr = 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

#计算树的层数
def getTreeDepth(myTree):
    maxDepth = 0
    firstStr = 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

#在父子结点间填充文本信息
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,va="center",ha="center",rotation=30)

def plotTree(myTree,parentPt,nodeTxt):
    numLeafs = getNumLeafs(myTree)
    depth = getTreeDepth(myTree)
    firstStr = myTree.keys()[0]
    cntrPt = (plotTree.xOff + (1.0+float(numLeafs))/2.0/plotTree.totalW,plotTree.yOff)
    plotMidText(cntrPt,parentPt,nodeTxt)#在父子结点间填充文本信息
    plotNode(firstStr,cntrPt,parentPt,decisionNode)#绘制带箭头的注释
    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,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()