I’ve been learning to use R and it’s been making my job a lot easier.  Sometimes, though, I get stuck on the silliest things.  One problem I ran into very early on was adding more than one set of points to a plot.  Even with the many instructions and examples, I still couldn’t figure this simple problem out!  Even more frustrating was that sometimes it seemed to work and other times it didn’t.

Then I figured out the difference between when it worked and when it didn’t –  (for anyone else with this problem) xlim and ylim MUST be specified in the original plot parameters.  As excited as I was to figure this out, I’m also a little embarrassed it was so hard for me!