How to find indices of maximum and minimum elements in a numpy matrix

Question

I want to find the indices of maximum and minimum elements in each row and column of a matrix. What Python function should I use for it?

Answer 1

You can use Numpy's argmax() / argmin() functions that return the indexes of the first occurrences of the maximum/minimum values along the specified axis.

Here is an example:

>>> import numpy as np
>>> aa=np.matrix([[3,1,4,6],[12,45,6,9],[89,0,5,19]])
>>> aa.argmin(axis=0)
matrix([[0, 2, 0, 0]])
>>> aa.argmin(axis=1)
matrix([[1],
        [2],
        [1]])
>>> aa.argmax(axis=0)
matrix([[2, 1, 1, 2]])
>>> aa.argmax(axis=1)
matrix([[3],
        [1],
        [0]])