how to take specific data from 3 dims NDArray?

[dooothink]

Description

from mxnet import nd

#x is 2x3x4 
x = nd.array([
    [
        [1,2,3,4],
        [5,6,7,8],
        [9,10,11,12]
    ],
    [
        [13,14,15,16],
        [17,18,19,20],
        [21,22,23,24]
    ]
])
idx = nd.array([0,2])
y = x.take(idx,axis=1)
print(y)

out is :
[[[ 1. 2. 3. 4.]
[ 9. 10. 11. 12.]]

[[13. 14. 15. 16.]
[21. 22. 23. 24.]]]
<NDArray 2x2x4 @cpu(0)>

how can I get a NDArray 2x1x4 as below
[
[ [1,2,3,4] ],
[ [21,22,23,24] ]
]

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[szha]

Hi, I think what you need is gather_nd

x = nd.array([
    ...:     [
    ...:         [1,2,3,4],
    ...:         [5,6,7,8],
    ...:         [9,10,11,12]
    ...:     ],
    ...:     [
    ...:         [13,14,15,16],
    ...:         [17,18,19,20],
    ...:         [21,22,23,24]
    ...:     ]
    ...: ])
    ...: idx = nd.array([[0, 1], [0, 2]])
    ...: y = nd.gather_nd(x, idx)
    ...: print(y)
    ...:

[[ 1.  2.  3.  4.]
 [21. 22. 23. 24.]]
<NDArray 2x4 @cpu(0)>

[dooothink]

@szha thanks, gather_nd + reshape can make the data I need

y = nd.reshape(y,shape=(2,-1,4))

[[[ 1.  2.  3.  4.]]

 [[21. 22. 23. 24.]]]
<NDArray 2x1x4 @cpu(0)>

and another way as below

from mxnet import nd

x = nd.array([
    [
        [1,2,3,4],
        [5,6,7,8],
        [9,10,11,12]
    ],
    [
        [13,14,15,16],
        [17,18,19,20],
        [21,22,23,24]
    ]
])

y = nd.array([
    [
        [1],
        [0],
        [0]
    ],
    [
        [0],
        [0],
        [1]
    ]
])
z = nd.broadcast_mul(x,y)
z = nd.sum(z,axis=1)
z = nd.reshape(z,shape=(2,-1,4))
print(z)

[[[ 1.  2.  3.  4.]]

 [[21. 22. 23. 24.]]]
<NDArray 2x1x4 @cpu(0)>