Finding local maxima/minima with Numpy in a 1D numpy array

Question

Can you suggest a module function from numpy/scipy that can find local maxima/minima in a 1D numpy array? Obviously the simplest approach ever is to have a look at the neare

Answer 1

In SciPy >= 0.11

import numpy as np
from scipy.signal import argrelextrema

x = np.random.random(12)

# for local maxima
argrelextrema(x, np.greater)

# for local minima
argrelextrema(x, np.less)

Produces

>>> x
array([ 0.56660112,  0.76309473,  0.69597908,  0.38260156,  0.24346445,
    0.56021785,  0.24109326,  0.41884061,  0.35461957,  0.54398472,
    0.59572658,  0.92377974])
>>> argrelextrema(x, np.greater)
(array([1, 5, 7]),)
>>> argrelextrema(x, np.less)
(array([4, 6, 8]),)

Note, these are the indices of x that are local max/min. To get the values, try:

>>> x[argrelextrema(x, np.greater)[0]]

scipy.signal also provides argrelmax and argrelmin for finding maxima and minima respectively.