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Method one:

findpeaks function

PKS = findpeaks(data)

[PKS,locs] = findpeaks(data) — the number of peaks corresponding to PKS and locs

[…] = findpeaks(data,’minpeakheight’, MPH)– MPH sets the minimum peakheight

[…] = findpeaks(data,’minpeakdistance’, MPD)– MPD sets the minimum interval between two peaks

[…] = findpeaks(data,’threshold’,th)

[…] = findpeaks(data,’npeaks’,np)

[…] = findpeaks(data,’sortstr’, STR)

the command findpeaks is used to findpeaks of a vector that is greater than the value of two adjacent elements.
for example:
a=[1 3 2 5 6 8 5 3];
findpeaks(a),
returns 3 8
[v,l]= findbb2 (a),
returns
v=3 8
l=2 6
if a is a matrix, the values and locations of the peaks are listed in column search order.
For more information, see Help FindPeaks
Disadvantages:
You can only find the peak, you can’t find the trough.

Reproduced indicate the source: http://write.blog.csdn.net/postlist

Method 2:
IndMin=find(diff(sign(diff(data)))> 0) + 1;
IndMax=find(diff(sign(diff(data)))< 0) + 1;

where,
IndMin, data(IndMin) corresponds to the trough data
IndMax,data(IndMax) corresponds to the crest data

>> a=[1 3 2 5 6 8 5 3]

a =

     1     3     2     5     6     8     5     3

>> IndMax=find(diff(sign(diff(a)))<0)+1

IndMax =

     2     6

>> a(IndMax)

ans =

     3     8

>> IndMin=find(diff(sign(diff(a)))>0)+1

IndMin =

     3

>> a(IndMin)

ans =

     2

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