Prawn::Graph aims to add this functionality to Prawn by using the 
native PDF drawing tools Prawn exposes and a friendly single-method 
call to draw the graph.

The graphs and the values plotted and drawn are all relatively sized
within the bounds of the width and height you have set and should 
scale pretty well to any size of value. Of course, if things do end
up looking too squashed, you can always just make your graph bigger.

At the moment, only Bar and Line charts are implemented, with others
coming soon. Both charts work in mostly the same way.

WWW: http://ryanstenhouse.eu