基于《机器学习实战》第八章的案例,乐高玩具预测的实例,但是因为原始的Google网页已经失效,所以这里用新的网页进行提取。
完整的代码及注释:
#-*- coding: utf-8 -*-
from numpy import *
from BeautifulSoup import BeautifulSoup
# 从页面读取数据,生成retX和retY列表
def scrapePage(retX, retY, inFile, yr, numPce, origPrc):
# 打开并读取HTML文件
fr = open(inFile);
soup = BeautifulSoup(fr.read())
i=1
# 根据HTML页面结构进行解析
currentRow = soup.findAll('table', r="%d" % i)
while(len(currentRow)!=0):
currentRow = soup.findAll('table', r="%d" % i)
title = currentRow[0].findAll('a')[1].text
lwrTitle = title.lower()
# 查找是否有全新标签
if (lwrTitle.find('new') > -1) or (lwrTitle.find('nisb') > -1):
newFlag = 1.0
else:
newFlag = 0.0
# 查找是否已经标志出售,我们只收集已出售的数据
soldUnicde = currentRow[0].findAll('td')[3].findAll('span')
if len(soldUnicde)==0:
print "item #%d did not sell" % i
else:
# 解析页面获取当前价格
soldPrice = currentRow[0].findAll('td')[4]
priceStr = soldPrice.text
priceStr = priceStr.replace('$','') #strips out $
priceStr = priceStr.replace(',','') #strips out ,
if len(soldPrice)>1:
priceStr = priceStr.replace('Free shipping', '')
sellingPrice = float(priceStr)
# 去掉不完整的套装价格
if sellingPrice > origPrc * 0.5:
print "%d\t%d\t%d\t%f\t%f" % (yr,numPce,newFlag,origPrc, sellingPrice)
retX.append([yr, numPce, newFlag, origPrc])
retY.append(sellingPrice)
i += 1
currentRow = soup.findAll('table', r="%d" % i)
# 依次读取六种乐高套装的数据,并生成数据矩阵
def setDataCollect(retX, retY):
scrapePage(retX, retY, '/setHtml/lego8288.html', 2006, 800, 49.99) #这里的网页的地址需要进行调整为自己电脑上保存的地址
scrapePage(retX, retY, '/setHtml/lego10030.html', 2002, 3096, 269.99)
scrapePage(retX, retY, '/setHtml/lego10179.html', 2007, 5195, 499.99)
scrapePage(retX, retY, '/setHtml/lego10181.html', 2007, 3428, 199.99)
scrapePage(retX, retY, '/setHtml/lego10189.html', 2008, 5922, 299.99)
scrapePage(retX, retY, '/setHtml/lego10196.html', 2009, 3263, 249.99)
# 计算给定lambda值得回归系数
def ridgeRegres(xMat,yMat,lam=0.2):
# 使用矩阵运算实现146页的回归系数计算公式
xTx = xMat.T*xMat
denom = xTx + eye(shape(xMat)[1])*lam
# 判断是否为奇异矩阵
if linalg.det(denom) == 0.0:
print "This matrix is singular, cannot do inverse"
return
ws = denom.I * (xMat.T*yMat)
return ws
# 计算回归系数矩阵
def ridgeTest(xArr,yArr):
# 初始化X和Y矩阵
xMat = mat(xArr); yMat=mat(yArr).T
# 对X和Y矩阵进行标准化
# 计算所有特征的均值
yMean = mean(yMat,0)
# 特征值减去各自的均值
yMat = yMat - yMean
# 标准化X矩阵数据
# 获得均值
xMeans = mean(xMat,0)
# 获得方差
xVar = var(xMat,0)
# 标准化方法:减去均值除以方差
xMat = (xMat - xMeans)/xVar
# 计算回归系数30次
numTestPts = 30
wMat = zeros((numTestPts,shape(xMat)[1]))
for i in range(numTestPts):
ws = ridgeRegres(xMat,yMat,exp(i-10))
wMat[i,:]=ws.T
return wMat
# 交叉验证测试岭回归
def crossValidation(xArr,yArr,numVal=10):
# 获得数据点个数,xArr和yArr具有相同长度
m = len(yArr)
indexList = range(m)
errorMat = zeros((numVal,30))
# 主循环 交叉验证循环
for i in range(numVal):
# 随机拆分数据,将数据分为训练集(90%)和测试集(10%)
trainX=[]; trainY=[]
testX = []; testY = []
# 对数据进行混洗操作
random.shuffle(indexList)
# 切分训练集和测试集
for j in range(m):
if j < m*0.9:
trainX.append(xArr[indexList[j]])
trainY.append(yArr[indexList[j]])
else:
testX.append(xArr[indexList[j]])
testY.append(yArr[indexList[j]])
# 获得回归系数矩阵
wMat = ridgeTest(trainX,trainY)
# 循环遍历矩阵中的30组回归系数
for k in range(30):
# 读取训练集和数据集
matTestX = mat(testX); matTrainX=mat(trainX)
# 对数据进行标准化
meanTrain = mean(matTrainX,0)
varTrain = var(matTrainX,0)
matTestX = (matTestX-meanTrain)/varTrain
# 测试回归效果并存储
yEst = matTestX * mat(wMat[k,:]).T + mean(trainY)
# 计算误差
errorMat[i,k] = ((yEst.T.A-array(testY))**2).sum()
# 计算误差估计值的均值
meanErrors = mean(errorMat,0)
minMean = float(min(meanErrors))
bestWeights = wMat[nonzero(meanErrors==minMean)]
# 不要使用标准化的数据,需要对数据进行还原来得到输出结果
xMat = mat(xArr); yMat=mat(yArr).T
meanX = mean(xMat,0); varX = var(xMat,0)
unReg = bestWeights/varX
# 输出构建的模型
print "the best model from Ridge Regression is:\n",unReg
print "with constant term: ",-1*sum(multiply(meanX,unReg)) + mean(yMat)
lgX = []
lgY = []
setDataCollect(lgX, lgY)
crossValidation(lgX, lgY, 10)
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
- 11
- 12
- 13
- 14
- 15
- 16
- 17
- 18
- 19
- 20
- 21
- 22
- 23
- 24
- 25
- 26
- 27
- 28
- 29
- 30
- 31
- 32
- 33
- 34
- 35
- 36
- 37
- 38
- 39
- 40
- 41
- 42
- 43
- 44
- 45
- 46
- 47
- 48
- 49
- 50
- 51
- 52
- 53
- 54
- 55
- 56
- 57
- 58
- 59
- 60
- 61
- 62
- 63
- 64
- 65
- 66
- 67
- 68
- 69
- 70
- 71
- 72
- 73
- 74
- 75
- 76
- 77
- 78
- 79
- 80
- 81
- 82
- 83
- 84
- 85
- 86
- 87
- 88
- 89
- 90
- 91
- 92
- 93
- 94
- 95
- 96
- 97
- 98
- 99
- 100
- 101
- 102
- 103
- 104
- 105
- 106
- 107
- 108
- 109
- 110
- 111
- 112
- 113
- 114
- 115
- 116
- 117
- 118
- 119
- 120
- 121
- 122
- 123
- 124
- 125
- 126
- 127
- 128
- 129
- 130
- 131
- 132
- 133
- 134
- 135
- 136
- 137
- 138
- 139
- 140
- 141
- 142
- 143
- 144
- 145
- 146
- 147
- 148
- 149
- 150
- 151
- 152
- 153
- 154
- 155
- 156
- 157
- 158
- 159
亲测有效