masking a multidimensional array - numpy

Question

I have two identical arrays of size (2,3,2)

[[[1, 7],
  [2, 8], 
  [3, 9]],

 [[4, 10],
  [5, 11],
  [6, 12]]]

stored in a multidimensional array

>>> a  =  np.array([[[[ 1,  1],
              [ 7,  7]],

             [[ 2,  2],
              [ 8,  8]],

             [[ 3,  3],
              [ 9,  9]]],

            [[[ 4,  4],
              [10, 10]],

             [[ 5,  5],
              [11, 11]],

             [[ 6,  6],
              [12, 12]]]])

>>> a.shape
(2, 3, 2, 2)

I'm trying to mask the sub arrays in a with m:

>>> m  =  np.array([[[1, 0],
                 [0, 0],
                 [1, 1]],

                [[1, 1],
                 [0, 1],
                 [0, 0]]])

which should result in:

[[[[ 1,  1],
   [ 0,  0]

   [ 0,  0],
   [ 0,  0],

   [ 3,  3],
   [ 9,  9]]

  [[ 4, 4],
   [10, 10],

   [ 0,  0],
   [11,  11],

   [ 0,  0],
   [ 0,  0]]]

I tried to use np.concatenate and np.append eg, np.prod(np.concatenate([a,m],axis=0))

but none of my solutions worked.

hpaulj · Accepted Answer · 2019-11-21 19:40:20Z

2

Expand the dimensions of m so it broadcasts with a:

In [183]: a*m[...,None]                                                         
Out[183]: 
array([[[[ 1,  1],
         [ 0,  0]],

        [[ 0,  0],
         [ 0,  0]],

        [[ 3,  3],
         [ 9,  9]]],


       [[[ 4,  4],
         [10, 10]],

        [[ 0,  0],
         [11, 11]],

        [[ 0,  0],
         [ 0,  0]]]])

answered Nov 21, 2019 at 19:40

hpaulj

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