graphics.off() #erases previous graphics
x=seq(.4,4,.1); y=log(x^2+1/x^2)
plot(x,y,type="p") #p for points
plot(x,y,type="l") #l for line
plot(x,y,type="s") #l for step
plot(x,y,type="p",pch=2) #pch : type of points 
##ylim=c(ay,by), xlim=c(ax,bx) : bounds of the axes
##lty : type of line, col : color, main : title
x=rnorm (20); y=rexp (20)
plot(x,y,col="red",ylim=c(-0.5 , 5),xlim=c(-3,2))  
points(x+.5,y-1,pch=2,col="blue") #add points
legend("topleft",c("plot_1","plot_2"),col=c("red","blue"),
       pch=c(1,2))
lines(x,y, lty=2, col="green") #add line
abline (h=3,col="yellow",lty=1)#add horizontal line
abline (v=-1.3,col="aquamarine2")#add vertical line
abline (a=1,b=1,col="coral3")#add oblique line
text(-2,2 ,"commentary");title("Example curves")