How to find the maximum of peaks ?

Question

Ramesh Bala 2021-8-18

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1436222-how-to-find-the-maximum-of-peaks

评论： Ramesh Bala 2021-8-19

采纳的回答： Yazan

ZT2.mat

在 MATLAB Online 中打开

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

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Answer 1

Yazan 2021-8-18

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1436222-how-to-find-the-maximum-of-peaks#answer_770089

在 MATLAB Online 中打开

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