This is my first Question here, let me know if I could've done anything better.
I'm trying to do a element-wise operation between two arrays, but the broadcasting wont work like I want it to.
I have an array of shape (N,4).
square_list = np.array([[1,2,255,255], [255,255,4,4], [255,255,8,8], [255,255,16,16], [255,255,8,4], [255,1,8,8], [1,255,8,8]], dtype='B')
I also have an array of shape (4,).
square = np.array([1, 8, 8, 1], dtype='B')
What I am able to do is compare my square
against each element in the square_list
and it is being broadcast into shape (N,4) as expected.
Now I want to compare my square
in each possible rotation against the square_list
. I've written a function which returns an array of shape (4,4), which contains each possible rotation.
square.rotations
array([[1, 8, 8, 1],
[1, 1, 8, 8],
[8, 1, 1, 8],
[8, 8, 1, 1]], dtype=uint8)
I know how to do this using a loop. I'd prefer however to use an element-wise operator that returns my desired shape.
What I get:
rotations & square_list
ValueError: operands could not be broadcast together with shapes (4,4) (6,4)
What I'd like to get:
rotations & square_list
array([[[1, 0, 8, 1],
[1, 8, 0, 0],
[1, 8, 8, 0],
[1, 8, 0, 0],
[1, 8, 8, 0],
[1, 0, 8, 0]],
[[1, 0, 8, 8],
[1, 1, 0, 0],
[1, 1, 8, 8],
[1, 1, 0, 0],
[1, 1, 8, 0],
[1, 1, 8, 8]],
[[0, 0, 1, 8],
[8, 1, 0, 0],
[8, 1, 0, 8],
[8, 1, 0, 0],
[8, 1, 0, 0],
[8, 1, 0, 8],
[0, 1, 0, 8]],
[[0, 0, 1, 1],
[8, 8, 0, 0],
[8, 8, 0, 0],
[8, 8, 0, 0],
[8, 8, 0, 0],
[8, 0, 0, 0],
[0, 8, 0, 0]]], dtype=uint8)
This is just to visualize what I want, I don't particularly care about the order of the axis'. A shape of either (4, N, 4) or (N, 4, 4) would be great. I have the feeling that this can be achieved easily by just reshaping one of the input arrays but I couldn't figure it out.
Thanks in advance!
CodePudding user response:
Add an extra dimension to rotations:
square_list & rotations[:,None]
output:
array([[[1, 0, 8, 1],
[1, 8, 0, 0],
[1, 8, 8, 0],
[1, 8, 0, 0],
[1, 8, 8, 0],
[1, 0, 8, 0],
[1, 8, 8, 0]],
[[1, 0, 8, 8],
[1, 1, 0, 0],
[1, 1, 8, 8],
[1, 1, 0, 0],
[1, 1, 8, 0],
[1, 1, 8, 8],
[1, 1, 8, 8]],
[[0, 0, 1, 8],
[8, 1, 0, 0],
[8, 1, 0, 8],
[8, 1, 0, 0],
[8, 1, 0, 0],
[8, 1, 0, 8],
[0, 1, 0, 8]],
[[0, 0, 1, 1],
[8, 8, 0, 0],
[8, 8, 0, 0],
[8, 8, 0, 0],
[8, 8, 0, 0],
[8, 0, 0, 0],
[0, 8, 0, 0]]], dtype=uint8)