How do I pick the largest peaks in a region?

Asked by Bharath Lohray on 21 Jun 2017

Latest activity Edited by Bharath Lohray on 21 Jun 2017

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The following MATLAB code takes in multiple peak coordinates and heights and eliminates lesser peaks that are within a certain distance threshold of the highest peak of the vicinity. Is there a better way to implement this code? Does a more efficient algorithm exist?

Code

    function [ the_peaks ] = max_peaks( peak_list, vicinity_threshold )
    %MAX_PEAKS(peak_list, vicinity_threshold) returns the highest peaks within
    %the vicinity specified by the vicinity_threshold.
    %
    %   peak_list is an array with rows defined by [x,y, amplitude]
    %
    %   vicinity_threshold is the distance within which all lesser peaks are
    %   killed.
    sorted_peaks=sortrows(peak_list,3,'desc');
    the_peaks=zeros(size(sorted_peaks));     % Preallocate
    peak_idx=1;
    while(~isempty(sorted_peaks))
        the_peaks(peak_idx,:)=sorted_peaks(1,:);     %The greatest peak.
        peak_idx=peak_idx+1;
        D=pdist2(sorted_peaks(1:end,1:2),sorted_peaks(1,1:2));     %Distance to other peaks
        np=D<vicinity_threshold;     % Peaks in the vicinity
        sorted_peaks(np,:)=[];     % Kill peaks in the vicinity
    end
    %
    the_peaks(~any(the_peaks,2),:)=[];     % clear preallocated extras
    end

example

    test_peaks=[1,1,0.5; 5,5,0.9; 5,1,0.6; 300,300,0.2; 303,303,0.7; 1,100,0.9; 1,104,0.95; 1,250,.7; 1,200,.75];
    mP=max_peaks(test_peaks,10)
    scatter (test_peaks(:,1),test_peaks(:,2),'o');
    hold on
    scatter (mP(:,1),mP(:,2),'*');

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Answer by Michelle Hirsch on 21 Jun 2017

If you are up for replacing the peak finding, and have Signal Processing Toolbox, you could consider trying findpeaks. The MinPeaksDistance option keeps just the highest peak in a neighborhood of peaks.

1 Comment

Bharath Lohray on 21 Jun 2017

I just tried and discovered that findpeak() does not work on matrices. It needs a vector :-(

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