import sys
from numpy import NaN, Inf, arange, isscalar, asarray, array
[docs]def peakdet(v, delta, x = None):
"""
Converted from MATLAB script at http://billauer.co.il/peakdet.html
Returns two arrays
.. code-block:: matlab
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 = []
minpos = []
maxpos = []
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))
maxpos.append(mxpos)
mn = this
mnpos = x[i]
lookformax = False
else:
if this > mn+delta:
mintab.append((mnpos, mn))
minpos.append(mnpos)
mx = this
mxpos = x[i]
lookformax = True
# return array(maxtab), array(mintab)
return maxpos, minpos
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()