GUI Library for Visualizing Data

Hi, the Haskell language is fairly new to me, so please pardon me if this is a frequently asked question, but I wasn't able to find an answer myself. I'm looking for a library that allows me to visualize data under X11 screen, for instance as a pie chart or as a bar chart. I seem to recall that something like that was available for the GTK toolkit, but has this library been ported to Haskell? Or any other library? I'd appreciate any pointers! -peter