交 叉
以cars数
attach(cars)head(cars)summary(lm(dist~speed,cars))n<-nrow(cars)s<-sample(1:n,round(n/2))traindata<-cars[s,]testdata<-cars[-s,]
summary(lm.tr<-lm(dist~speed,traindata))ptedist.lm<-predict(lm.tr,testdata)ptrdist.lm<-predict(lm.tr,traindata)temse<-sum(ptedist.lm-testdata$dist)^2/nrow(testdata)trmse<- sum(ptrdist.lm-traindata$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=lis ...