求和前的 numpy 数组扩展

Question

我想将加载数据的数组的维度增加 1。在总结神经网络的隐藏层之前。不知怎的，我想例如：

之前： x = np.arange(12).reshape(2,2,3)

[[[ 0  1  2]
  [ 3  4  5]]

 [[ 6  7  8]
  [ 9 10 11]]]

之后：新形状 (2,2,3,3)

[[[[ 0.  1.  2.]
   [ 0.  1.  2.]
   [ 0.  1.  2.]]

  [[ 3.  4.  5.]
   [ 3.  4.  5.]
   [ 3.  4.  5.]]]


 [[[ 6.  7.  8.]
   [ 6.  7.  8.]
   [ 6.  7.  8.]]

  [[ 9. 10. 11.]
   [ 9. 10. 11.]
   [ 9. 10. 11.]]]]

我不想使用“for”循环语句，我更喜欢数组函数或数组操作。在此先感谢您的帮助！

Answer 1

重塑并使用np.broadcast_to

x_out = np.broadcast_to(x[...,None,:], (2,2,3,3))

Out[1131]:
array([[[[ 0,  1,  2],
         [ 0,  1,  2],
         [ 0,  1,  2]],

        [[ 3,  4,  5],
         [ 3,  4,  5],
         [ 3,  4,  5]]],


       [[[ 6,  7,  8],
         [ 6,  7,  8],
         [ 6,  7,  8]],

        [[ 9, 10, 11],
         [ 9, 10, 11],
         [ 9, 10, 11]]]])

Answer 2

repeat 给出了想要的结果。结果不像“broadcast_to”那样具有内存效率，但它可能更容易理解：

In [78]: x = np.arange(12).reshape(2,2,3)

In [81]: x1 = x[:,:,None,:].repeat(3,2)
In [82]: x1
Out[82]: 
array([[[[ 0,  1,  2],
         [ 0,  1,  2],
         [ 0,  1,  2]],

        [[ 3,  4,  5],
         [ 3,  4,  5],
         [ 3,  4,  5]]],


       [[[ 6,  7,  8],
         [ 6,  7,  8],
         [ 6,  7,  8]],

        [[ 9, 10, 11],
         [ 9, 10, 11],
         [ 9, 10, 11]]]])

另一个，x[:,:,None]*np.ones((3,1),int)

求和前的 numpy 数组扩展

numpy array extension before sum

python

arrays

numpy

dimension

multidimensional-array