fitting envelope peak points

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Ancalagon8
Ancalagon8 on 22 May 2020
Commented: Image Analyst on 19 Jun 2020
I am facing some problems trying to create a fitting curve that will pass through maximum peaks. I tried findpeaks
findpeaks(Sig)
hold all
plot(Sig,'k')
as well as envelope
[up, lo] = envelope(Sig,'peak');
plot(Sig, 'o-k');
hold on
plot(up,'r');
plot(lo,'b');
legend ('bb','up','down')
grid
How can i create a fitting curve which will pass through max peak points? Will a solution be to export peaks into a new array, plot them and then create a fitting curve or there is another way?
Thanks in advance!

Accepted Answer

Image Analyst
Image Analyst on 22 May 2020
Just try interp1() or spline(). Pass in your peak points and then the x values of the whole array, something like
[peakValues, indexes] = findpeaks(Sig);
yOut = spline(indexes, peakValues, 1:length(Sig));
plot(yOut, 'b-', 'LineWidth', 2);
grid on;
Let me know if it works. Attach your Sig data if it doesn't. Accept this answer if it does.
  11 Comments
Ancalagon8
Ancalagon8 on 18 Jun 2020
@Image Analyst would it be possible to adjust the above code for power law and not exponential fitting?
Image Analyst
Image Analyst on 18 Jun 2020
Yes. Did you try to change the model? It's not hard. See attached.

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More Answers (1)

Ancalagon8
Ancalagon8 on 19 Jun 2020
Edited: Ancalagon8 on 19 Jun 2020
@Image Analyst thank you once more for your answer!I tried to change the code so as to receive something like this but i did not work for me:
  1 Comment
Image Analyst
Image Analyst on 19 Jun 2020
Wow, that's bizarre, but we've seen it before. See this link.
It seems to be related to the OpenGL renderer.
Or see this answer.

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