Plot 2 graphs in same plot in R?

Question

I would like to plot y1 and y2 in the same plot.

x  <- seq(-2, 2, 0.05)
y1 <- pnorm(x)
y2 <- pnorm(x,1,1)
plot(x,y1,type="l",col="red")
plot(x,y2,type="l",col="green")

But when I do it like this, they are not plotted in the same plot together.

In Matlab can one do hold on, but does anyone know how to do this in R?

Answer 1

lines() or points() will add to the existing graph, but will not create a new window. So you'd need to do

plot(x,y1,type="l",col="red")
lines(x,y2,col="green")

Answer 2

If you are using base graphics (i.e. not lattice/ grid graphics), then you can mimic MATLAB's hold on feature by using the points/lines/polygons functions to add additional details to your plots without starting a new plot. In the case of a multiplot layout, you can use par(mfg=...) to pick which plot you add things to.