On 9/19/2008 9:32 AM, john crepezzi wrote: > Is it possible to see if a plot is already open before I call lines()? I don't think so. You can see if a graphics device is open by looking at dev.cur(), but I don't think there's a test for plot.new(). I'd just wrap the call in try() if you're not sure it will work. Duncan Murdoch