I was wondering if anyone knew of a simple way to implement graphing in an iPhone/iPad application. I've spent quite a bit of time googling and can't seem to find any sort of a solution. Maybe I'm just searching with the wrong terms since a lot of consumers are asking about "graphing" in terms of using their applications, not developing them, the search-space is rather polluted.

It seems like a lot of iPad/iPhone applications have embedded graphs... and I can't imagine that every developer has invented their own graphing engine from the ground up. Or, maybe they have... Does anyone have any suggestions?