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# endolith/peakdet.m

Last active Jun 3, 2022
Peak detection in Python [Eli Billauer]
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 function [maxtab, mintab]=peakdet(v, delta, x) %PEAKDET Detect peaks in a vector % [MAXTAB, MINTAB] = PEAKDET(V, DELTA) finds the local % maxima and minima ("peaks") in the vector V. % MAXTAB and MINTAB consists of two columns. Column 1 % contains indices in V, and column 2 the found values. % % With [MAXTAB, MINTAB] = PEAKDET(V, DELTA, X) the indices % in MAXTAB and MINTAB are replaced with the corresponding % X-values. % % A point is considered a maximum peak if it has the maximal % value, and was preceded (to the left) by a value lower by % DELTA. % Eli Billauer, 3.4.05 (Explicitly not copyrighted). % This function is released to the public domain; Any use is allowed. maxtab = []; mintab = []; v = v(:); % Just in case this wasn't a proper vector if nargin < 3 x = (1:length(v))'; else x = x(:); if length(v)~= length(x) error('Input vectors v and x must have same length'); end end if (length(delta(:)))>1 error('Input argument DELTA must be a scalar'); end if delta <= 0 error('Input argument DELTA must be positive'); end mn = Inf; mx = -Inf; mnpos = NaN; mxpos = NaN; lookformax = 1; for i=1:length(v) this = v(i); if this > mx, mx = this; mxpos = x(i); end if this < mn, mn = this; mnpos = x(i); end if lookformax if this < mx-delta maxtab = [maxtab ; mxpos mx]; mn = this; mnpos = x(i); lookformax = 0; end else if this > mn+delta mintab = [mintab ; mnpos mn]; mx = this; mxpos = x(i); lookformax = 1; end end end
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 import sys from numpy import NaN, Inf, arange, isscalar, asarray, array def peakdet(v, delta, x = None): """ Converted from MATLAB script at http://billauer.co.il/peakdet.html Returns two arrays function [maxtab, mintab]=peakdet(v, delta, x) %PEAKDET Detect peaks in a vector % [MAXTAB, MINTAB] = PEAKDET(V, DELTA) finds the local % maxima and minima ("peaks") in the vector V. % MAXTAB and MINTAB consists of two columns. Column 1 % contains indices in V, and column 2 the found values. % % With [MAXTAB, MINTAB] = PEAKDET(V, DELTA, X) the indices % in MAXTAB and MINTAB are replaced with the corresponding % X-values. % % A point is considered a maximum peak if it has the maximal % value, and was preceded (to the left) by a value lower by % DELTA. % Eli Billauer, 3.4.05 (Explicitly not copyrighted). % This function is released to the public domain; Any use is allowed. """ maxtab = [] mintab = [] if x is None: x = arange(len(v)) v = asarray(v) if len(v) != len(x): sys.exit('Input vectors v and x must have same length') if not isscalar(delta): sys.exit('Input argument delta must be a scalar') if delta <= 0: sys.exit('Input argument delta must be positive') mn, mx = Inf, -Inf mnpos, mxpos = NaN, NaN lookformax = True for i in arange(len(v)): this = v[i] if this > mx: mx = this mxpos = x[i] if this < mn: mn = this mnpos = x[i] if lookformax: if this < mx-delta: maxtab.append((mxpos, mx)) mn = this mnpos = x[i] lookformax = False else: if this > mn+delta: mintab.append((mnpos, mn)) mx = this mxpos = x[i] lookformax = True return array(maxtab), array(mintab) if __name__=="__main__": from matplotlib.pyplot import plot, scatter, show series = [0,0,0,2,0,0,0,-2,0,0,0,2,0,0,0,-2,0] maxtab, mintab = peakdet(series,.3) plot(series) scatter(array(maxtab)[:,0], array(maxtab)[:,1], color='blue') scatter(array(mintab)[:,0], array(mintab)[:,1], color='red') show()

### pelissarisergioo commented Nov 17, 2018

Thank you for this snippet, it works perfectly in my implementation.

Thanks man!

### TravisH0301 commented Mar 10, 2021

Thanks for sharing your code! It works very well for my project.