Modify element of index based on array iteratively in n-dimensional array

Question

I have a base array base = [0,1,2,3] which contains elements of the set {0,...,k} (where k is 3 in this example). I also have another array modif which is a n dimensional array, where n is the number of distinct elements in base.

I want to add one iteratively to an element of the modif array, given by indexes of base, so if base = [0,1,2,3] a function must add one to modif[0,1,2,3].

I tried doing something like

probs[b for b in base] += 1

or

probs[(b for b in base)] += 1

or even

for b in base:
    sel = probs[b]
sel += 1

But the problems are that in the first and second, it is not valid syntax, and in the third, the sel is actually a copy of probs[b], not the same actual objects, so the change is not done in probs.

Kasravnd · Accepted Answer · 2017-03-24 13:29:41Z

1

You don't need a comprehension just convert the indices to tuple. Here is an example:

In [42]: a
Out[42]: 
array([[[ 2,  2,  2,  3,  4],
        [ 5,  6,  7,  8,  9],
        [10, 11, 12, 13, 14]],

       [[15, 16, 17, 18, 19],
        [20, 21, 22, 23, 24],
        [25, 26, 27, 28, 29]]])

In [43]: b
Out[43]: [0, 1, 2]

In [44]: a[tuple(b)]
Out[44]: 7

In [45]: a[tuple(b)] += 100

In [46]: a
Out[46]: 
array([[[  2,   2,   2,   3,   4],
        [  5,   6, 107,   8,   9],
        [ 10,  11,  12,  13,  14]],

       [[ 15,  16,  17,  18,  19],
        [ 20,  21,  22,  23,  24],
        [ 25,  26,  27,  28,  29]]])

answered Mar 24, 2017 at 13:29

Kasravnd

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