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Thread: QwtPlot filter

  1. #1
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    Default QwtPlot filter

    Hi,

    I want to represent a certain amount of points about (51.2k) on the graph.
    My graph length is 1000 pixels, and of course I can not display all the points.

    So I want to use the appropriate filter that he could display a graph representative of the data.

    I figured my particular filter formula based on an average.
    For any particular set of points I make an average and the result I draw on the graph.

    My question is there common filter I can use? And where I can find an articles about this filtering subject?

    I use Qwt 6.0 on Qt platform
    Windows xp sp3

    Thanks!

  2. #2
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    Default Re: QwtPlot filter

    what is this common filter you're talking about???? You've to create your own filter. So create it by yourself.....

    implement it......
    Heavy Metal Rules. For those about to rock, we salute you.
    HIT THANKS IF I HELPED.

  3. #3
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    Default Re: QwtPlot filter

    Quote Originally Posted by simonb View Post
    My question is there common filter I can use?
    For line plots one possible option is to use the Douglas Peucker algo, that is implemented in Qwt and available as QwtWeedingCurveFitter. The algo is too slow to apply it each time your curve gets painted ( using QwtPlotCurve::setCurveFitter() ), but you can reduce the number of points before passing them as curve points.

    In combination with polygon clipping ( QwtPlotCurve::ClipPolygons ) you can implement a data object that returns different sets of points according to the current scales. For large ranges you can reduce the number of points using weeding and for small ranges ( zoomed in ) polygon clipping will reduce the number of points to be painted. This leads to a fast and responsive plot without losing details.

    This topic has been discussed a couple of times on this forum as "different levels of detail".

    HTH,
    Uwe

  4. The following user says thank you to Uwe for this useful post:

    simonb (10th July 2012)

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