all4=read.table("/Users/pcaragea/teaching/Stat401/STAT401F07/Compute/anscombe.txt",header=TRUE)
attach(all4)


MS1=lm(y[set==1]~x[set==1])
MS2=lm(y[set==2]~x[set==2])
MS3=lm(y[set==3]~x[set==3])
MS4=lm(y[set==4]~x[set==4])
pdf("/Users/pcaragea/teaching/Stat401/STAT401F07/Compute/Anscombe_R.pdf")
#plots:
plot(x[set==1],y[set==1],pch=20,xlab="X",ylab="Y",main="Set 1")
abline(MS1$coef)
plot(x[set==2],y[set==2],pch=20,xlab="X",ylab="Y",main="Set 2")
abline(MS2$coef)
plot(x[set==3],y[set==3],pch=20,xlab="X",ylab="Y",main="Set 3")
abline(MS3$coef)
plot(x[set==4],y[set==4],pch=20,xlab="X",ylab="Y",main="Set 4")
abline(MS4$coef)

#residual plots
plot(MS1,which=1,pch=20)
plot(MS2,which=1,pch=20)
plot(MS3,which=1,pch=20)
plot(MS4,which=1,pch=20)

#cooks' distance
plot(MS1,which=4,pch=20)
plot(MS2,which=4,pch=20)
plot(MS3,which=4,pch=20)
plot(MS4,which=4,pch=20)

#to compute just Cook's distance:
cooks.distance(MS1)
cooks.distance(MS2)
cooks.distance(MS3)
cooks.distance(MS4)

dev.off()