I'm sure this is a simple problem, but I've been going around in circles several days trying to figure this out. Here's my code.http://pastebin.com/n83dGhG4 Basically, I'm trying to get my pyqt4 button signal to execute the plot command (line 122). A lot of this code was copied from the matplotlib example page. If I uncomment line 148, the figure will successfully plot. I don't understand why what I'm doing on line 122 isn't equivalent to line 148. thx for your help.Matt