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Thread: number of visible points of a curve

  1. #1
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    Default number of visible points of a curve

    Hi,

    does Qwt provide a function that returns the number of currently visible points of a curve (depending on the scale of x and y).
    I didn't find any in the documentation. What's the best way to get it?

    I would use QwtScaleDiv::lowerBound() and QwtScaleDiv::upperBound() for x and y and parse over all data of a curve
    and check if QwtScaleDiv::contains(double x-value) and QwtScaleDiv::contains(double y-value).

    Is there a better way?

    Regards
    Stefan

  2. #2
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    Default Re: number of visible points of a curve

    Without having an extra spatial index ( f.e a quadtree ) and not knowing any specific characteristics of the data ( f.e ordered according x ) iterating over all points is all you can do.

    Uwe

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