Extract sub array from d-dimensional array given indices for each dimension

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Michael Van de Graaff
编辑： Michael Van de Graaff 2022-5-21
Suppose I have a d-dimensional array A which is size d_1 by d_2 by....by d_d and for each dimension i have a index vector vd_i such that vd_i(1)>=1 and vd_i(end)<= size(A, i). How do I extract the sub array A(vd_1,vd_2,...,vd_3) when d is arbitrary?
Edit: as mentioned by the wonderful Matt J, I meant that 1<= vd_i(j)<= size(A,i) for all i,j.
  2 个评论
Matt J
Matt J 2022-5-20
编辑：Matt J 2022-5-21
and for each dimension i have a index vector vd_i such that vd_i(1)>=1 and vd_i(end)<= size(A, i).
I think what you really mean is 1<= vd_i(j)<= size(A,i) for all i,j. If that's not what you meant then, well, you should check that it's true, because it's a requirement in any subscript indexing operation.

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采纳的回答

Matt J
Matt J 2022-5-20
编辑：Matt J 2022-5-20
If you have your vd_i in a cell array V={vd_1,vd_2,...,vd_d}, you can do
A(V{:})

更多回答（2 个）

Voss
Voss 2022-5-20
Ran in:
% random 4-D (4x8x5x10) array A:
d_siz = [4 8 5 10];
A = randn(d_siz);
size(A)
ans = 1×4
4 8 5 10
% make the index vectors for each dimension
% into a cell array:
vd = {[2 3] [1 3 5 7] [2 3 4] 4:8};
% index into A in each dimension:
A_subs = A(vd{:});
size(A_subs)
ans = 1×4
2 4 3 5
dpb
dpb 2022-5-20
Did you try the obvious???
Smallish example, but works in general...
>> d=3;A=reshape(1:4^d,4,4,[]) % make up a sample array to play with that can read
>> A
A(:,:,1) =
1 5 9 13
2 6 10 14
3 7 11 15
4 8 12 16
A(:,:,2) =
17 21 25 29
18 22 26 30
19 23 27 31
20 24 28 32
A(:,:,3) =
33 37 41 45
34 38 42 46
35 39 43 47
36 40 44 48
A(:,:,4) =
49 53 57 61
50 54 58 62
51 55 59 63
52 56 60 64
>>
>> v1=2:3;v2=v1;v3=v1; % pick middle two of each dimension
>> A(v1,v2,v3)
ans(:,:,1) =
22 26
23 27
ans(:,:,2) =
38 42
39 43
>>
is, by inspection, the array elements of 2nd, 3rd plane and the central four elements of each, respectively.

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