Create new matrix based on the index in an array

Question

let's say I have a 1D array a:

a = np.array([0.75,0.85,0.95,0.1])

I also have a 2x2 index array b:

b=np.array([[0,2,0,3],[1,2,1,0]])

Now I want to create a 2x2 array c, where each element in c will be chosen from array a based on the index from array b, for example, array c will look like this:

array([[0.75, 0.95, 0.75, 0.1 ],
       [0.85, 0.95, 0.85, 0.75]])

I tried to use np.take_along_axis() to achieve this but failed. Any suggestions?

You should read the docs: numpy.org/doc/stable/user/basics.indexing.html#index-arrays — suvayu
– suvayu, Commented Jul 14, 2021 at 16:27

orlp · Accepted Answer · 2021-07-14 16:13:12Z

3

a[b]

edited Jul 14, 2021 at 16:13

answered Jul 14, 2021 at 16:06

orlp

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Comments

Christian · Accepted Answer · 2021-07-14 16:17:58Z

0

another way to do it ia with a loop for or list comprehension

c = np.array([a[x] for n in b for x in n])
print(c)

output

array([0.75, 0.95, 0.75, 0.1 , 0.85, 0.95, 0.85, 0.75])

answered Jul 14, 2021 at 16:17

Christian

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