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Peak detection in Python [Eli Billauer]
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
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
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pelissarisergioo commented Nov 17, 2018

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

@cgi1
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cgi1 commented Feb 4, 2020

Thanks man!

@TravisH0301
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TravisH0301 commented Mar 10, 2021

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

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