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How do I index an array with varying dimension?

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runtime_error
runtime_error 2024-2-9
评论： Stephen23 2024-2-9
I have a function Y = func(X)
X can be any dimension >=2. Inside the function, I need to index X by the first dimension. X(index, :) or X(index, :, :) depending on the dimension. I know I can check the dimension like this:
if ndims(X) == 2
X(index, :) = ....
elseif ndims(x) == 3
X(index, :, :) = ..
end
Is there a more efficient way?

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采纳的回答

Walter Roberson
Walter Roberson 2024-2-9
Ran in:
If you use a trailing dimension of : to index, then the result has the proper size but with the dimension "unwrapped"
A = ones(3,4,5);
B = A(2,:);
size(B)
ans = 1×2
1 20
You can leave it like that for computations, or you can reshape() it
sz = size(A);
sz(1) = 1;
C = reshape(B,sz);
size(C)
ans = 1×3
1 4 5
Alternately....
indx = repmat({':'}, 1, ndims(A));
indx{1} = 2;
D = A(indx{:});
size(D)
ans = 1×3
1 4 5

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