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Local Peaks

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Local Peaks

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18 Sep 2009 (Updated )

Find local peaks or troughs in a vector

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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)
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Comments and Ratings (9)
06 Sep 2013 zhiyang  
21 Jun 2012 Wilson  
19 Apr 2011 Jeremy

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

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.

01 Jun 2010 Christos Saragiotis

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  
28 Apr 2010 Christopher Hummersone

or rather,

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

01 Apr 2010 Christopher Hummersone

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

25 Sep 2009 Herve

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

Updates
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

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