Custom coordinates into an array

Question

0 个投票

Hi,

This problem is getting me really crazy right now.

I'm trying to figure a way to make this work elegantly.

A is a N x N x N x...x N array (N is repeated M times).

N and M are integers greater than 2.

Assume a given i in {1,...,M} and a given j in {1,...N}.

I'm looking for a way to design a function that will receive A,N,M,i,j and will return

A(:,:,...,:,j,:...,:)

where j is at the i-th coordinate.

I.E. all elements who have j as their i-th coordinate, stored into a Nx...xN (M-1 times) array.

I have spent hours trying to find an elegant way to do this.

and still haven't found a lot in matlab's doc (sub2ind might come in handy eventually)

I also tried to design ':,...,:,j,:,...:' as a string and tried to pass it as an argument to A() but it does not seem to work.

I'm a bit stuck in here and I could really use a tip on this !

Thank you for your time !

M

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Answer 1

Andrei Bobrov 2013-10-10

1 个投票

ii = repmat({':'},1,M);
ii(i) = {j};
out = A(ii{:});

Matthieu 2013-10-10

Good job. Works perfectly fine. First time I hear about this repmat function. Could have saved me from a lot of trouble in previous codes. Thanks !