error: too many open devices

Hi,

R stops running my code and gives me the following error message:

Error in win.graph(width = 8.5, height = 11) :
        too many open devices

My code calls for R to produce over 100 graphs, but it stops running and gives
me this error message after about 60. I'm sure there's an easy fix. Anyone
know?

Many thanks in advance, Kate