limit the search for maximums to a specific region

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Vittorio Locatelli
Vittorio Locatelli 2022-5-12
评论： Voss 2022-5-13
Good morning,
I am writing because, as the title suggests, I need to limit the search for maximums in a specific region. What I have to do is basically obtain a specific section from an image to find the color spectrum and from this identify the peaks approximately from 1500 to 3000 pixels.
In the findpeaks tab I have not found anything that can do for me.
I turn to you hoping for constructive help.
Thanks in advance for the answers.
% % mostra imgrifpixelscaled
figure
imshow(imgrifassps)
% % cattura punti di riferimento; nota: considera 10mm, mantieniti al centro della figura e prendi il primo punto a sinistra e il secondo punto a destra, infine la sezione di riferimento assoluta e poi relativa
[x,y]=ginput(4);
% % crea sezione di riferimento assoluto
sezionerifass=imgrifassps(round(y(3)),:);
% % fitting sezione rif ass
[xData, yData]=prepareCurveData( [], sezionerifass );
ft=fittype( 'smoothingspline' );
opts=fitoptions( 'Method', 'SmoothingSpline' );
opts.SmoothingParam=0.001;
[fitresult,gof]=fit( xData, -yData, ft, opts );
% % crea variabile sezione di riferimento assoluto fittata
sezionerifassfit=fitresult(xData);
% % trova picchi sezione di riferimento assoluto fittata
[prifass,locsrifass]=findpeaks(sezionerifassfit,"MinPeakHeight",-100,"NPeaks",7);

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Voss
Voss 2022-5-13
Ran in:
Instead of inputting the entire array into findpeaks, you can simply input the part of the array you want to search, and then adjust the outputted indices appropriately.
% a signal with some peaks
t = 0:0.01:8*pi;
y = sin(t);
plot(t,y)
ylim([-1.1 1.1]);
hold on
% find the locations of the peaks in y
[~,idx] = findpeaks(y)
idx = 1×4
158 786 1415 2043
% plot them in red
plot(t(idx),y(idx),'ro','MarkerFaceColor','r')
% now find the peaks just among index 500 to index 1500 of y
[~,idx] = findpeaks(y(500:1500))
idx = 1×2
287 916
% adjust the indices of the peaks
% (index 1 in y(500:1500) corresponds to index 500 in y)
idx = idx+499
idx = 1×2
786 1415
% plot them in green
plot(t(idx),y(idx),'g.')
% show the search region for reference
xline(t([500 1500]),'--')
  2 个评论
Vittorio Locatelli
Vittorio Locatelli 2022-5-13
Thank you very much, now that you have told me the solution is quite simple. Thanks again.
Voss
Voss 2022-5-13
You're welcome!
If everything makes sense, please click 'Accept This Answer'. Otherwise, let me know any questions you have. I appreciate it!

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