How to transpose xAxis and yAxis for QwtPlotSpectrogram?

[Marco7]

Hi everybody,

is there a way to transpose the xAxis and the yAxis (e.g. xAxis pointing up, yAxis pointing to right) in a QwtPlotSpectrogram.

The reason why I don't simply change the data is that I want to make a fast animation of a large matrix and with

setValueMatrix(QVector.mid(0,i*n_cols),n_cols)

setValueMatrix(QVector.mid(0,i*n_cols),n_cols)

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I can very efficiently extract a sub-matrix but then the animation is row-wise instead of column-wise.

Thanks a lot
Marco

[Uwe]

Maybe deriving from QwtRasterData makes more sense than using QwtMatrixRasterData in your situation.

But if you want to use QwtMatrixRasterData you can simply:

YourRasterData: public QwtMatrixRasterData
{
public:
    ....
 
    virtual double value( double x, double y ) const
    {
        return QwtMatrixRasterData::value( y, x );
    }
};

YourRasterData: public QwtMatrixRasterData
{
public:
    ....

    virtual double value( double x, double y ) const
    {
        return QwtMatrixRasterData::value( y, x );
    }
};

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Uwe

[Marco7]

Hi Uwe,

Thanks a lot. Your solution worked fine.

By the way I'm really impressed by the speed of qwt. I used vtk before which is good for 3D graphics but for 2D qwt is much better.

Best regards,
Marco