回归（强影响点）

lijuanamy

states<-as.data.frame(state.x77[,c("Murder","Population","Illiteracy","Income","Frost")])
fit<-lm(Murder~Population+Illiteracy+Income+Frost,data=states)
cutoff<-4/(nrow(states)-length(fit$coefficients)-2)
plot(fit,which=4,cook.levels=cutoff)
plot()函数中的cook.levels有什么用?上面的plot函数与plot(fit,which=4)做出的图形是一模一样的。



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