graphic showing categories

Hello,

first of all, thanks a lot for developping this great software !

Though there is somethng i'd like to do but didn't find how, maybe it is not implemented :
I would like to see a graphic showing the amount of expenses per category / sub category, with a line of different color for each category.
With that, I would follow my expenses trough time by category : oups, this month I spent a lot in restaurants, or for fuel, or ..., in a single graph.

thanks !