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### Highlights from Local Peaks

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# Local Peaks

### Christopher Hummersone (view profile)

18 Sep 2009 (Updated )

Find local peaks or troughs in a vector

File Information
Description

LOCALPEAKS Find local peaks and troughs in a vector

SYNTAX

peaks = localpeaks(X)
peaks = localpeaks(X,MODE)

DESCRIPTION

peaks = localpeaks(X) locates the local peaks in vector X.

peaks = localpeaks(X,MODE) locates local features specified by MODE. MODE can be set to 'peaks' (default), 'troughs' in order to identify local troughs or 'both' in order to identify both local peaks and troughs.

Acknowledgements

Writing Fast Matlab Code inspired this file.

This file inspired Peaks Picking.

MATLAB release MATLAB 7.4 (R2007a)
06 Sep 2013 zhiyang

### zhiyang (view profile)

21 Jun 2012 Wilson

### Wilson (view profile)

19 Apr 2011 Jeremy

### Jeremy (view profile)

I don't like not having a blank line after the last line of code. Just kidding, awesome job on this function. Very simple, intuitive, and fast.

01 Jun 2010 Christopher Hummersone

### Christopher Hummersone (view profile)

Thanks for your comment Christos, I hadn't noticed this behaviour (I had been using it with long signals). I have fixed the function to address your first remark, and the code will now correctly identify peaks and troughs in a vector like [0 5 -5 5 0] with the 'both' option. I have not addressed your second comment since, as you alluded to, this is a plateaux and not a true peak.

Comment only
01 Jun 2010 Christos Saragiotis

### Christos Saragiotis (view profile)

Very good and an excellent example of terse programming.

I have two remarks though:
1. when selecting the 'both' option some peaks or troughs may be lost. E.g consider the vector [0, 5 -5, 5, 0]. Clearly -5 is a trough but localpeaks will not pick it.
2. if we consider again the vector [ 0 5 5 5 0], localpeaks will pick the first and last 5 as a peak but not the second one. I'm not sure if this was intentional but the way I see it it should either pick all of them or none.

25 May 2010 michael scheinfeild

### michael scheinfeild (view profile)

28 Apr 2010 Christopher Hummersone

### Christopher Hummersone (view profile)

or rather,

y = zeros(size(x)); peaks = localpeaks(x);
y(peaks) = x(peaks);

Comment only
01 Apr 2010 Christopher Hummersone

### Christopher Hummersone (view profile)

I didn't really see the point, if you want the value you can just do for example:
y = x(localpeaks(x));

Comment only
25 Sep 2009 Herve

### Herve (view profile)

Brillant !
You could have added an extra output which gives the values of the local peaks or throughs.

27 Apr 2010

added the 'both' option, updated help, acknowledged other submission

29 Apr 2010

Fixed a silly mistake, removed index output to bring the function more in line with MATLAB conventions (find(localpeaks(x)) would do the same), added an error trap

27 May 2010

Updated description

01 Jun 2010

Updated to address Christos Saragiotis' comment