QWT plot with autoscaling shows negative values in y-axis

[manikandan]

Hi,

I have a QWT plot which shows only positive data values as a curve. I want autoscaling to be done since the values are not fixed in a range. But when autoscaling is enabled for y-left axis, then y-axis starts with negative values. how can i avoid this?

setAxisAutoScale(QwtPlot::yLeft,true);

I tried changing void QwtPlot::updateAxes() in my own class but facing issues because of d_axisData[axisId] private data.

Thanks

[Uwe]

Autoscaling means, that you want to calculate the scales from a given interval ( the bounding interval of all plot items having the QwtPlotItem::AutoScale flag enabled ). The algorithm for this calculation is implemented in the scale engine - usually QwtLinearScaleEngine::autoScale().

If you are not happy with the result of the algorithm you have 2 options:



overload QwtLinearScaleEngine::autoScale
not using autoscaling and doing setAxisScale instead


The code you would have to write is more or less the same.

Uwe