Finding local minima for a signal

488 views (last 30 days)
I have used the (findpeaks) function in Matlab in order to find the locations and the value of the peaks ( Local Maxima ) in the signal.
please, Is there any function to extract the local minimums of the following graph?

Accepted Answer

Walter Roberson
Walter Roberson on 8 Aug 2016
If you have a routine that can find local maxima, then to find local minima, apply the local maxima routine to the negative of the data. Like
findpeaks(-X_Segments{nn},'MinPeakDistance', 20)

More Answers (3)

Azzi Abdelmalek
Azzi Abdelmalek on 8 Aug 2016
Use
findpeaks(-your_signal)

Image Analyst
Image Analyst on 9 Aug 2016
You're probably okay with your data, but beware of findpeaks() if your max or min spikes have flat tops or bottoms. It will give only the first index. In that case you want to use the imregionalmin() function from the Image Processing Toolbox. Just look at this example with a min that has a flat bottom:
data = [ 1 3 4 2 2 2 4 4 5 6] % Flat bottom with value of 2 from indexex 4-6
[peakValues, indexesOfPeaks] = findpeaks(-data)
peakValues = -peakValues
minIndexes = imregionalmin(data)
data =
1 3 4 2 2 2 4 4 5 6
peakValues =
-2
indexesOfPeaks =
4
peakValues =
2
minIndexes =
1 0 0 1 1 1 0 0 0 0
  2 Comments
Image Analyst
Image Analyst on 9 Aug 2016
I don't know how to answer that question.

Sign in to comment.


shima tavakoli
shima tavakoli on 13 Feb 2018
my signal is asymmetric and its negative parts are different. how to deal with negative parts peaks then? cant negative the signal in this case!
  1 Comment
Image Analyst
Image Analyst on 13 Feb 2018
Who knows? You forgot to read this and forgot to attach your signal and a screenshot of it, so there's not much I can say, other than to write custom code to deal with it.

Sign in to comment.

Community Treasure Hunt

Find the treasures in MATLAB Central and discover how the community can help you!

Start Hunting!