Numpy reduce 3d array to 2d based on condition

Question

I have a 3d array like this:

array([[[ 0,  1],
        [ 0,  0]],

        [[ 0,  0],
        [ 6,  7]]])

What I am trying to do is reduce it to a 2d array like this:

array([[1, 0],
       [0, 1]])

Where there is a 1 for each sub-array of the original that had non-zero elements, and a 0 if all the elements of the corresponding sub-array were zero.

How can I do this cleanly, without loops?

Sayandip Dutta · Accepted Answer · 2021-01-19 19:19:37Z

1

You can use numpy.ndarray.any along the last axis (axis=-1):

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

        [[ 0,  0],
        [ 6,  7]]])

>>> arr.any(axis=-1).astype(int)
array([[1, 0],
       [0, 1]])

answered Jan 19, 2021 at 19:19

Sayandip Dutta

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