Find peaks not working on my data set

Question

Ashlyn McCann 2021-3-9

0
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https://ww2.mathworks.cn/matlabcentral/answers/767357-find-peaks-not-working-on-my-data-set

评论： Steve Eddins 2021-3-9

I am trying to find the first 5 peaks in the PSD plot of an acoustic signal. While I do not have any bugs in my code, it is not finding actual peaks and looks more like arbitrary locations. I will paste my code below:

M = movmean((PSD), 50);
[maxpks, maxloc]=findpeaks(PSD(1:2000),'MinPeakDistance',195,'MinPeakHeight',-50,'NPeaks',5);
figure(1)
plot(fp,PSD)
hold on
%O=2*f %%convert to octaves so the slope is in dB/octave
plot((maxloc), maxpks, 'r*')
hold off
sortpks=sort(maxpks);
[j,h]=size(sortpks);
J= [sortpks(j),sortpks(j-1),sortpks(j-2), sortpks(j-3), sortpks(j-4)]; %first five peak 
ML = maxloc(j-4:j); %first five peak location
ML=(ML)'; %%convert to octaves so the slope is in dB/octave
figure(2)
plot(ML,J,'r*')
 Fit = polyfit(ML,J,1); %linear regression 
 yfit = Fit(1)*ML+Fit(2); %equation of line 
 hold on
 plot(ML,yfit,'g-')
 slope=Fit(1)%spectral tilt

The picture above is a zoomed in version of figure 1 and it is just not detecting the peaks I need. Thank you in advanced for any help!

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Answer 1

Steve Eddins 2021-3-9

1
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在 MATLAB Online 中打开

I suspect the issue is with the x-coordinates that you are using to plot the peaks. You are plotting the peaks against the indices returned by findpeaks, but you are plotting PSD against x-coordinates in the variable fp. So, intead of this:

plot((maxloc), maxpks, 'r*')

Try this:

plot(fp(maxloc), maxpks, 'r*')