CODEWITHSUNDEEP
pythonarraysnumpy
BoltzmannBrain
BoltzmannBrain

Reputation: 5392

Python - Break numpy array into positive and negative components

I have numpy arrays of shape (600,600,3), where the values are [-1.0, 1.0]. I would like to expand the array to (600,600,6), where the original values are split into the amounts above and below 0. Some examples (1,1,3) arrays, where th function foo() does the trick:

>>> a = [-0.5, 0.2, 0.9]
>>> foo(a)
[0.0, 0.5, 0.2, 0.0, 0.9, 0.0]  # [positive component, negative component, ...]
>>> b = [1.0, 0.0, -0.3]  # notice the behavior of 0.0
>>> foo(b)
[1.0, 0.0, 0.0, 0.0, 0.0, 0.3]

Upvotes: 1

Views: 1357

Answers (1)

Peter Gibson
Peter Gibson

Reputation: 19554

Use slicing to assign the min/max to different parts of the output array

In [33]: a = np.around(np.random.random((2,2,3))-0.5, 1)

In [34]: a
Out[34]: 
array([[[-0.1,  0.3,  0.3],
        [ 0.3, -0.2, -0.1]],

       [[-0. , -0.2,  0.3],
        [-0.1, -0. ,  0.1]]])

In [35]: out = np.zeros((2,2,6))

In [36]: out[:,:,::2] = np.maximum(a, 0)

In [37]: out[:,:,1::2] = np.maximum(-a, 0)

In [38]: out
Out[38]: 
array([[[ 0. ,  0.1,  0.3,  0. ,  0.3,  0. ],
        [ 0.3,  0. ,  0. ,  0.2,  0. ,  0.1]],

       [[-0. ,  0. ,  0. ,  0.2,  0.3,  0. ],
        [ 0. ,  0.1, -0. ,  0. ,  0.1,  0. ]]])

Upvotes: 3

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