x<-c(80,100,120,140,160,180,200,220,240,260) y<-c(65,77,89,101,113,125,137,149,161,173) y1<-c(70,65,90,95,110,115,120,140,155,150) y2<-c(55,88,90,80,118,120,145,135,145,175) plot(x,y,cex=1.0, col="black") abline(lm(y~x),col="black") points(x,y1,cex=1.0, col="blue") points(x,y2,cex=1.0, col="red") abline(lm(y1~x),col="blue") abline(lm(y2~x),col="red",lty=2)