Indexing a multidimensional array with a matrix in Matlab

Question

How can I index the dimensions of an nd-array element using a 2d matrix, which records represent, which dimensions (representing slices or 2d matrices) take values ​​from?

I=ones(2)*2;
J=cat(3,I,I*2,I*3);

indexes = [1 3 ; 2 2] ;

therefore J is

J(:,:,1) =

 2     2
 2     2


J(:,:,2) =

 4     4
 4     4


J(:,:,3) =

 6     6
 6     6

it works easily using 2 for loops

for i=1:size(indexes,1)
     for j=1:size(indexes,2)
        K(i,j)=J(i,j,indexes(i,j));
    end
end

which gives the desired result

K =

 2     6
 4     4

but is there a way for vectoring / smart indexing?

%K=J(:,:,indexes)  --does not work

Answer 1

Just use linear indexing :

nElementsPerSlice = numel(indexes);

linearIndices = (1:nElementsPerSlice) + (indexes(:)-1) * nElementsPerSlice;

K = J(linearIndices);

Answer 2

you can use sub2ind to convert matrix indices to linear index

ind = sub2ind( size(J), [1 1 2 2], [1 2 1 2], [1 3 2 2]);
K = resize(J(ind), [2 2]);