Qwt is a graphics extension to the Qt GUI application framework. It provides a 2D plotting widget and more.
I would've recommended it if it wasnt for a confusing GUI.
Developers familiar with Qt know that its strengths lie in an easy to use API, extensive documentation and generally being a fairly comprehensive framework. Unfortunately, one thing the Qt framework is missing is an out of the box charting solution. This is where Qwt steps in. It is built upon Qt and offers a fair selection of 2d charts. Sounds good. Unfortunately it isn't. I have no doubt the author (Uwe Rathmann) is an experienced programmer, particularly with Qt, but Qwt shares non-of the user friendly advantages that Qt provides. The documentation is not easy to follow. The API is not intuitive. It is inefficient in many places. And is far from bug free. Qwt enjoys it's own sub section over at QtCentre where you will be able to interact directly with Uwe and another (rather terse) developer called Wysota. We use it because there is no alternative and we are not given time to roll our own (which I would love to do). If you love the ease at which you can use Qt do not expect the same experience from Qwt. Sadly, whilst Qwt is the best charting library for Qt, that does not mean it is good.