spectrogram example problem

[azcoder]

I modified the spectrogram example to plot a 10x10 unit image with the original 3x3 unit image inside it. I changed the axis values to be -5 to +5 for both the x & y axis and the constructor rectangle values to (-5, -5, 10, 10). I then enabled the top axis and disabled the bottom axis. The plot is clipped at about -4 to +4 on the x axis only when the axis is at the top. If it is at the bottom, it is plotted OK. Any way to fix this? Am I doing something wrong?

Here is the code:

class SpectrogramData: public QwtRasterData
{
public:
    SpectrogramData():
//        QwtRasterData(QwtDoubleRect(-1.5, -1.5, 3.0, 3.0))
        QwtRasterData(QwtDoubleRect(-5.0, -5.0, 10.0, 10.0))
    {
    }
 
    virtual QwtRasterData *copy() const
    {
        return new SpectrogramData();
    }
 
    virtual QwtDoubleInterval range() const
    {
        return QwtDoubleInterval(0.0, 10.0);
    }
 
    virtual double value(double x, double y) const
    {
        const double c = 0.842;
 
        const double v1 = x * x + (y-c) * (y+c);
        const double v2 = x * (y+c) + x * (y+c);
 
if ((x < -1.5 || x > 1.5) || (y < -1.5 || y > 1.5))
    return 0.0;     // return 0 outside 3 unit box
 
        return 1.0 / (v1 * v1 + v2 * v2);
    }
};
 
Plot::Plot(QWidget *parent):
    QwtPlot(parent)
{
    d_spectrogram = new QwtPlotSpectrogram();
 
#ifndef DO_TOP
enableAxis(xTop, true);
enableAxis(xBottom, false);
setAxisScale(QwtPlot::xTop, -5.0, 5.0);
#else
setAxisScale(QwtPlot::xBottom, -5.0, 5.0);
#endif
setAxisScale(QwtPlot::yLeft, -5.0, 5.0);
 
    QwtLinearColorMap colorMap(Qt::darkCyan, Qt::red);
    colorMap.addColorStop(0.1, Qt::cyan);
    colorMap.addColorStop(0.6, Qt::green);
    colorMap.addColorStop(0.95, Qt::yellow);
 
    d_spectrogram->setColorMap(colorMap);
 
    d_spectrogram->setData(SpectrogramData());
    d_spectrogram->attach(this);
 
..... the rest of the code is the same......

class SpectrogramData: public QwtRasterData
{
public:
    SpectrogramData():
//        QwtRasterData(QwtDoubleRect(-1.5, -1.5, 3.0, 3.0))
        QwtRasterData(QwtDoubleRect(-5.0, -5.0, 10.0, 10.0))
    {
    }

    virtual QwtRasterData *copy() const
    {
        return new SpectrogramData();
    }

    virtual QwtDoubleInterval range() const
    {
        return QwtDoubleInterval(0.0, 10.0);
    }

    virtual double value(double x, double y) const
    {
        const double c = 0.842;

        const double v1 = x * x + (y-c) * (y+c);
        const double v2 = x * (y+c) + x * (y+c);

if ((x < -1.5 || x > 1.5) || (y < -1.5 || y > 1.5))
    return 0.0;     // return 0 outside 3 unit box

        return 1.0 / (v1 * v1 + v2 * v2);
    }
};

Plot::Plot(QWidget *parent):
    QwtPlot(parent)
{
    d_spectrogram = new QwtPlotSpectrogram();

#ifndef DO_TOP
enableAxis(xTop, true);
enableAxis(xBottom, false);
setAxisScale(QwtPlot::xTop, -5.0, 5.0);
#else
setAxisScale(QwtPlot::xBottom, -5.0, 5.0);
#endif
setAxisScale(QwtPlot::yLeft, -5.0, 5.0);

    QwtLinearColorMap colorMap(Qt::darkCyan, Qt::red);
    colorMap.addColorStop(0.1, Qt::cyan);
    colorMap.addColorStop(0.6, Qt::green);
    colorMap.addColorStop(0.95, Qt::yellow);

    d_spectrogram->setColorMap(colorMap);

    d_spectrogram->setData(SpectrogramData());
    d_spectrogram->attach(this);

..... the rest of the code is the same......

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I also have included two jpeg files that show the normal bottom axis result and the invalid top axis result.

Thanks in advance for any help.

Jim

[Uwe]

Assuming you want the spectrogram displayed according to the top axis:

d_spectrogram->setAxis(QwtPlot::xTop, QwtPlot::yLeft);

d_spectrogram->setAxis(QwtPlot::xTop, QwtPlot::yLeft);

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Uwe

[azcoder]

Thank You! That made it work like I wanted.

Jim