I need a radial chart, but my version of Word/Powerpoint doesn't have it?

I need to be able to edit a radial-style chart, but my current version of Microsoft Office:Mac Edition doesn't have a radial chart. Is there another Macintosh program that I can use to edit a template of a radial chart, or is there a specific update I can find for Office? I'm looking for freeware, I don't have any money to spend!