find the point with the maximum third element in numpy array

Question

Dear all: if I have an array, let's say

a=np.asarray([[1,1,2],[2,3,1]])

is there any way to find the point with the greatest third element. For example, in this case, I want the code to return the second point which is [1,1,2].

Then what about the greatest second element which should return [2,3,1]

thanks a lot for your great help and advice.

@Chris, sorry for my wording. the first point is [1,1,2] and the second point is [2,3,1]. so the greatest third element is in point 1 which is 2 — yihao ren
– yihao ren, Commented Sep 21, 2020 at 4:20

Valdi_Bo · Accepted Answer · 2020-09-21 04:44:47Z

1

A more numpythonic (than in one of comments) way to get the answer, for any element of interest, is:

elemNo = 1
a[np.argmax(a[:, elemNo])]

Note that:

a[:, elemNo] retrieves the column of interest,
np.argmax(...) finds the index of the max value in this column.

So a[...] retrieves the whole row with just this index.

This solution should also work faster than map / lambda, what can be important especially for bigger arrays.

edited Sep 21, 2020 at 4:44

answered Sep 21, 2020 at 4:35

Valdi_Bo

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