Peak detection in TAChart ?
lazarus / 55-TAChart

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AL · 2019-11-14 18:23

Is there a way to detect peaks with TAChart in a TlineSeries?

Thanks,

Al

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Thaddy · 2019-11-14 18:31

You should not misuse the TaChart for that:TaChart is the presentation
layer, not the compute layer.
 You should detect peaks in the data before you display it. And that
is a simple max run.

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wp · 2019-11-14 18:56

No automatic peak detection, I agree with Thaddy.

There is a manual interactive peak detection with some limitations,
though. Look at example "distancedemo" in folder "demo/distance" of
your Lazarus installation, page "Fit": Select "Find peak" in the
"Measure" box, then, holding the RIGHT mouse button down, drag from
the somewhere below the peak to somewhere after the peak. The routine
will fit a parabola to the data in the range spanned by the mouse
range and display y and y value of the parabola's extremum.

Note, however, that this does not separate overlapping peaks or
subtract a varying background. Therefore, the peak producing the
shoulder near x=6 is reported at an incorrect value (7.75, but from
the construction of the curve it should be at 2*pi = 6.28; finding the
correct value requires more effort).

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AL · 2019-11-14 19:51

WP:  Thanks for pointing that demo.  This is interesting, I will study
that.

Quote from: Thaddy on November 14, 2019, 07:31:21 pmYou should not
misuse the TaChart for that:TaChart is the presentation layer, not the
compute layer.
 You should detect peaks in the data before you display it. And that
is a simple max run.
This is what I tought, but I wanted to ask, just in case.  This
package is so good, you never know.
At the moment, this is what I do, looking for max ( up to 3 peaks),
but I need something a little fancier.

Thank you both for your quick answers