OmniGraphSketcher is an iPad app that makes it easy to create gorgeous and precise graphs with lines, curves, shaded regions, and more. Instead of using specific equations, like a graphing calculator, OmniGraphSketcher let's you use multitouch gestures to chart your points and draw cuves and bar graphs.
The Omni Group is famous for their high quality, thoughtfully designed, and enormously useful productivity apps for iPhone, iPad, and Macs, including OmniFocus, OmniGraphSketcher, OmniGraffle, and OmniOutliner. They were one of the earliest high profile developers to go all-in on the iPad, bringing several of their premium apps to platform on launch day. Not believing the "consumption not creation" mantra of the usual suspects, they took cues from Apple on model controls and full screen workflows and re-imagined their apps until they became a way to almost finger-paint with productivity.