I just directly translated to Python from this MATLAB script, which I've also included here. The original is public domain, so my translation is, too.
Also see Frequency estimation methods in Python for interpolating to get sharp intersample peaks
sixtenbe has posted a more powerful version here
and there's a PyPI repo
| 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() |
Thanks for sharing your code! It works very well for my project.