Comments on: Finding Local Extrema

By: bshoelso

bshoelso — Wed, 08 Feb 2012 19:26:09 +0000

Sepid,
Click on the link to Extrema in the post above, then click to download Carlos’s package. Make sure those functions are on your MATLAB path, and you should be good to go.
Brett

By: sepid

sepid — Wed, 08 Feb 2012 19:17:43 +0000

hi, i have the same problem like sri,

how can i download the exterma funtion? could u plz send this for me?

By: Brett

Brett — Thu, 08 Sep 2011 13:16:34 +0000

Sri,
It sounds like you have a path issue. Make sure Carlos’s function is download and that it lives somewhere on your MATLAB path, or in the directory you’re currently working in.
Brett

By: Sri

Sri — Thu, 08 Sep 2011 03:11:15 +0000

I tried using the Carlos’s extrema code in Matlab, but it gives me the following error

??? Undefined function or method ‘extrema’ for input arguments of type ‘double’

Please help me out!

By: Aslak Grinsted

Aslak Grinsted — Thu, 25 Aug 2011 09:20:58 +0000

There is also the built-in function findpeaks from the signal processing toolbox:

http://www.mathworks.se/help/toolbox/signal/findpeaks.html

By: Brett

Brett — Thu, 02 Jun 2011 03:49:44 +0000

toto: Try extrema2, by Carlos Adrian Vargas Aguilera:

http://www.mathworks.com/matlabcentral/fileexchange/12275-extrema-m-extrema2-m

Cheers,
Brett

By: toto

toto — Mon, 30 May 2011 06:42:09 +0000

thank you for sharing this code. I have a question for you. How to finding local extrema in 2D data. Thank you

By: Brett

Brett — Thu, 15 Jul 2010 20:18:10 +0000

@Nara,
Hi Nara…hard to comment without seeing your data. Perhaps some filtering might be needed. Maybe even just a moving average filter might suffice.

By: Nara

Nara — Fri, 25 Jun 2010 20:34:36 +0000

I have a set of data that resembles a step; few data points, a jump and few more points. The problem here is that the trend of the points before or after the jump is not quite plateau. They may increase or decrease gradually (but the variation is still smaller than the jump). The “EXTREMA” function can capture some max. or min. points but not all. Do you have any idea how to get all the extremums?

By: Martin H.Skjelvareid

Martin H.Skjelvareid — Tue, 09 Feb 2010 16:39:38 +0000

I also highly recommend Eli Billauer’s algorithm “peakdet” (http://www.billauer.co.il/peakdet.html ). This algorithm only detects “major” local peaks, ignoring noise peaks. The result is somewhat similar to that of the smoothed data above, but the peaks are found in the original time series. The trick that Eli does is to accept only those extrema for which the amplitude changes significantly afterwards (Unfortunately, this is done in a for-loop traversing the data). I’ve found that this algorithm is usually more useful for my applications than algorithms returning all extrema.