Numpy array of indexes to array of elements

Question

I have a MxN numpy array containing ints, representing indexes of a big array of size K How do I convert efficiently my M*N array of indexes to an MxN array of elements?

Example :

K = ['a','b','c','d']
M = [[0,3],[2,1]]

Result :

[['a','d'],['c','b']]

Thank you!

........ K[M]?

Divakar
– Divakar

2018-11-05 14:14:06 +00:00
Commented Nov 5, 2018 at 14:14 — Divakar
– Divakar, Commented Nov 5, 2018 at 14:14
Welp, now I feel dumb. Thank you!

Adrien Nivaggioli
– Adrien Nivaggioli

2018-11-05 14:15:59 +00:00
Commented Nov 5, 2018 at 14:15 — Adrien Nivaggioli
– Adrien Nivaggioli, Commented Nov 5, 2018 at 14:15

willeM_ Van Onsem · Accepted Answer · 2018-11-05 14:15:03Z

4

We can make numpy arrays from these lists:

import numpy as np

k = np.array(K)
m = np.array(M)

and then perform a mapping with k[m]:

>>> k[m]
array([['a', 'd'],
       ['c', 'b']], dtype='<U1')

Here for every element in m, we thus "replace" it with the element stored in k at the index of the original value of m at that location.

answered Nov 5, 2018 at 14:15

willeM_ Van Onsem

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