qwt log scale Limits

[jav321]

Hi,

I am plotting a curve with magnitude in dBs and frequency from 0Hz to 20Khz on linear scale. I generate a simple linear frequency array. Now I want to view my Curve on a typical log scale that is used in audio players. But I don't know how ?

I tried adding this to my code.

QwtLog10ScaleEngine *qwtlog = new QwtLog10ScaleEngine();
 
 
     plot->setAxisScaleEngine(QwtPlot::xBottom, qwtlog);

QwtLog10ScaleEngine *qwtlog = new QwtLog10ScaleEngine();


     plot->setAxisScaleEngine(QwtPlot::xBottom, qwtlog);

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This does work but my x axis scale starts at 1E-100 and ends at 1. I want to change its limits so that it goes from 0 to 20KHz like this

http://machrone.home.comcast.net/~ma...tave_sweep.gif

Can anyone help me as to what should I do ?

[Nomad_Tech]

This thread is pretty old so I hope you've found a solution by now but from the documentation of 'QwtLog10ScaleEngine' it seems you should be calling: qwtlog->autoScale(<maxNumSteps>, 0, 20000, <stepSize>)