Is there a function for changing all row values in a numpy array?

Question

I have got a 5 by 5 numpy array and a list of 3 values

a = np.array[([[0,4,5,8,2],
 [2,3,4,1,3],
 [2,3,4,1,3],
 [2,3,4,1,3],
 [2,3,4,1,3]])

BC = np.array([0,3,4])

with this condition, every row and column of the BC must be 0. In this case, the first, fourth and fifth row and column. The output therefore needs to be

[0,0,0,0,0
0,3,4,0,0
0,3,4,0,0
0,0,0,0,0
0,0,0,0,0]

Of course it is possible to do a[0,0] = 0 and then for every place in the matrix, but I want to use a for loop because the original matrix is 12*12. Thanks for your help!

Does this answer your question? Modify a particular row/column of a NumPy array — Ahmed AEK
– Ahmed AEK, Commented Sep 26, 2022 at 22:16

Ahmed AEK · Accepted Answer · 2022-09-26 22:55:24Z

1

you just have to slice the array then assign it to zeros as follows:

a = np.array[([[0,4,5,8,2],
 [2,3,4,1,3],
 [2,3,4,1,3],
 [2,3,4,1,3],
 [2,3,4,1,3]])

BC = np.array([0,3,4])

a[BC,:] = 0
a[:,BC] = 0

[BC,:] losely translates to "indicies of rows as in BC and all columns".

answered Sep 26, 2022 at 22:55

Ahmed AEK

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1 Comment

user12581768 Over a year ago

Ahhh yess that was fairly easy, thanks!!

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