[R] How do I plot multiple XY plots on the same graph

[George Chen]

Hello,
I have multiple data sets I would like to plot on the same XY scatterplot.
The data sets have in common the same Y values.
Could somebody tell me how to do this?
I tried par(T=new)   (I think this was it) but it literally overlays plots on each other.

Thanks in advance.

George