View Full Version : Question about qwt polar's Azimuth scale

7th October 2008, 15:42

I want to set my polar plot's Azimuth scale to 0~360 degree clock-wise and display 0 degree at the start instead of 360. Attached is my current plot showing 360 degree. Anybody knows how to change it to 0 degree(clock-wise)?

Thank you!

9th October 2008, 07:23
plot->setScale(QwtPolar::Azimuth, 360.0, 0.0, 15.0);

Looking into QwtRoundScaleDraw::drawLabel you can see, that ticks that are mapped to a position >= 360 degree ( 0.0 is mapped to 360 ) are skipped. Unfortunately this is hardcoded.

I'm afraid you need to derive your own type of scale draw:

class YourScaleDraw: public QwtRoundScaleDraw
virtual QwtText label(double value) const
return QwtRoundScaleDraw::label(::fmodf(value, 360.0) );

plot->setScaleDraw(QwtPolar::Azimuth, new YourScaleDraw);