交叉验证.ppt

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1、交 叉 验 证,以cars数据为例,attach(cars)head(cars)summary(lm(distspeed,cars)n-nrow(cars)s-sample(1:n,round(n/2)traindata-carss,testdata-cars-s,summary(lm.tr-lm(distspeed,traindata)ptedist.lm-predict(lm.tr,testdata)ptrdist.lm-predict(lm.tr,traindata)temse-sum(ptedist.lm-testdata$dist)2/nrow(testdata)trmse-sum(

2、ptrdist.lm-traindata$dist)2/nrow(traindata)nls.tr-nls(log(dist)xmid*log(speed),data=traindata,start=list(xmid=0)nls.tr-nls(log(dist)log(xmid*speed),data=traindata,start=list(xmid=0.1)summary(nls.tr),ptedist.nls-predict(nls.tr,testdata)ptrdist.nls-predict(nls.tr,traindata)temse-sum(ptedist.nls-testdata$dist)2/nrow(testdata)trmse-sum(ptrdist.nls-traindata$dist)2/nrow(traindata)训练集合测试集交换,