The url shortening service I'm building needs to display some basic click stats to users: # of clicks, conversions, referring domains, and country (filterable by a date range). I'll possibly want more advanced stats in the future.

Is there existing open source software that will allow me to pass events to it and then easily display a bar or line graph of that event (for example, a line graph of "conversions" between two specified dates). It seems like something like this should exist and would be much easier then building the whole thing from scratch.

I know there are graphing scripts, but that still requires me to format the data (usually as an xml file) and then pass it to the graph. I'm looking for something a bit more complete, which I can just feed the events and then it does everything else.