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pythonnumpykeymaxelementwise-operations

Element-wise maximum with key

is there a more efficient way to perform element-wise maximum with key?

import numpy as np
a = np.array([-2, 2, 4, 0])
b = np.array([-3,-5, 2, 0])
c = np.array([ 1, 1, 1, 1])

mxs = np.empty((4,))
for i in range(4):
    mxs[i] = max([a[i], b[i], c[i]], key=abs)

>>> mxs
array([-3., -5.,  4.,  1.])

Unfortunately, numpy.maximum does not offer a key parameter, as it would be nice to be able to do something similar with: np.maximum.reduce([a,b,c])

Solution

  • You can use:

    arr = np.array([a,b,c])
arr[np.argmax(np.abs(arr), axis=0), np.arange(arr.shape[1])]