Plotting graphs in Qt

[Computer Hater]

Hi,
I want to plot graphs in my program to display the results of a calculation.
I've been trying regular QGraphicsView functionality, but have been having difficulties getting it to work.
So far I've been ignoring this 'Qwt' label that has its own forum segment, but from what I'm reading now it seems that Qwt is exactly for that purpose. But I can't find a description in the Qt documentation of what Qwt is and how it works.

Can someone confirm whether or not I should be using Qwt and tell me where I can find documentation on that ?

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A second issue that has been puzzling me:
I've read in the documentation that QGraphicsSimpleTextItem has a 'scale()' function that returns the current scale and a 'setScale(qreal) scale' function that sets one scale factor.
But when I type 'item->scale' in QtCreator, it also suggests another function, 'scale(qreal sx, qreal sy)', that apparently scales both dimensions invidually, but that I can't find in the documentation.

So, my questions are:
- Why is this apparently not in the documentation ?
- How do these two functions interact ? I've experimented with combining them, but I don't understand the results I get.

Thank you !