I have following indices
indices = array([[ 0, 0],
[ 1, 1],
[ 5, 3],
[ 7, 9]])
I want to update a 2d numpy array with these indices as one
img = np.zeros((12,12), np.uint8)
I tried the following
img[indices] = 1
indices_x = indices[:, 0]
indices_y = indices[:, 1]
img[np.ix_(indices_x,indices_y)] = 1
Try specifying the x and y indices separately.
In [0]: img[indices[:,0], indices[:,1]] = 3
In [1]: img
Out[1]:
array([[3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 3, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]], dtype=uint8)
Alternatively, you can give a tuple or list:
In [2]: new_inds = tuple(zip(*indices))
In [3]: new_inds
Out[3]: ((0, 1, 5, 7), (0, 1, 3, 9))
In [4]: img[new_inds] = 4
In [5]: img
Out[5]:
array([[4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 4, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 4, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 4, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0],
[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]], dtype=uint8)
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