How to find the maximum of peaks ?

I want to find the first maximum 4 peaks in loop.My code finds all the peaks,how can I find only 4 and plot them ?

A= load ('ZT2.mat');

figure
for i= 1:1:300

    s3=  abs(fft( A.A1(:,i)));

    subplot (3,2,1)
    plot (s3((1:end/2)));
    
    subplot (3,2,2)
    [pkSA{i},locSA{i}]=findpeaks(s3); 
    plot ( (locSA{i}),(pkSA{i}));
    title('Peaks ZT1');
    
    drawnow
    pause(0.1)
end

Answer 1

[Yazan]

Below, I am proposing an implementation of what I understood to be your task. You have to experiment with the findpeaks multiple options to find a setting good for your data.

clc, clear

load ('ZT2.mat');

figure

fftData = abs(fft(A1, [], 2));
N = size(fftData, 2);
fftData = [fftData(:, 1:N/2), fftData(:, 1)];
freq = linspace(0, 0.5, N/2+1);

locSA = cell(1, size(A1, 1));
pkSA = cell(1, size(A1, 1));
 
Np = 4;
sortP = 'descend';
minPeakDis = 1;

for i=1:size(fftData,1)
    
    [pkSA{i}, locSA{i}] = findpeaks(fftData(i,:), 'NPeaks', 4, 'SortStr', sortP, ...
        'MinPeakDistance', minPeakDis);
    
    subplot (1, 2, 1)
    plot(freq, fftData(i,:)); xlabel('Normalized frequency')
    ylabel('Amplitude'), title('Positive spectrum')
    hold on, plot(freq(locSA{i}), pkSA{i}, 's', 'MarkerSize', 5, 'MarkerEdgeColor', 'g',...
        'MarkerFaceColor', 'g'); grid minor, hold off
    
    subplot (1, 2, 2)
    stem(freq(locSA{i}), pkSA{i}, 'Marker', 's', 'MarkerSize', 7, 'MarkerEdgeColor', 'g',...
        'MarkerFaceColor', 'g'); xlabel('Normalized frequency')
    ylabel('Amplitude'), title('Spectral peaks locations'), grid minor
    
    drawnow
    pause(1)
end

[Ramesh Bala]

This is perfect .Thanks Yazan

this the key that I was expecting especially 'SortStr', sortP, ...

'MinPeakDistance', minPeakDis