limit the search for maximums to a specific region

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);

Answer 1

[Voss]

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]),'--')

[Vittorio Locatelli]

Thank you very much, now that you have told me the solution is quite simple. Thanks again.

[Voss]

You're welcome!

If everything makes sense, please click 'Accept This Answer'. Otherwise, let me know any questions you have. I appreciate it!