Extract peaks and troughs from a curve

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Mustafa Sobhy
Mustafa Sobhy 2019-7-29
评论： Star Strider 2019-7-29
How to extract only peaks and troughs from a curve
2.jpg

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Star Strider
Star Strider 2019-7-29
If you want to identify the individual peaks and troughs, use islocalmax and islocalmin, or findpeaks on the positive and negative versions of your signal respectively:
[pks, pklocs] = findpeaks(s);
[troughs,trlocs] = findpeaks(-s);
where ‘s’ is youir signal vector.
  2 个评论
Mustafa Sobhy
Mustafa Sobhy 2019-7-29
So how can I rearrange peaks and troughs consecutively like (peak, trough, peak, trough, ...) ?
Thanks!!
Star Strider
Star Strider 2019-7-29
As always, my pleasure!
Create a matrix of the peaks, troughs and locations, then use sortrows:
[pks, pklocs] = findpeaks(s); % Original Peaks
[troughs,trlocs] = findpeaks(-s); % Original Troughs
pktr = [pklocs(:), pks(:); trlocs(:) -troughs(:)]; % Location, Value Matrix
pktrs = sortrows(pktr); % Location, Value Matrix Sorted By Location
Since with findpeaks the troughs are detected using the negative of the original vector, their amplitudes in the ‘pktr’ matrix are negated to correct for that, presenting the actual values.
The sortrows function sorts by default on the first column. If you use a different configuration for ‘pktr’ you need to specify the column for the locations so that sortrows know which one to sort on.

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