numpy更新數組索引

Question

我有以下指數

indices = array([[ 0,  0],
   [ 1,  1],
   [ 5,  3],
   [ 7,  9]])

我想將這些索引作為一個更新2d numpy數組

img = np.zeros((12,12), np.uint8)

我嘗試了以下

img[indices] = 1
indices_x = indices[:, 0]
indices_y = indices[:, 1]
img[np.ix_(indices_x,indices_y)] = 1

Answer 1

嘗試分別指定x和y索引。

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)

另外，您可以給出一個元組或列表：

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)