MATLAB: Expand vector along third dimension

arraymatrix

My question is simply, but I cannot figure out how to do it.

Assume I have a vector K=[K_1,..,K_n] then I would like to create a three dimensional matrix M with first dimension equal to x, second dimension equal to y and third dimension equal to n such that M(:,:,1)=K1*ones(x,y), M(:,:,2)=K2 * ones(x,y) etc. I know of course I can loop, but I am expecting a neat one-liner exists.

Best Answer

I have a matrix S which is x times y. Then I would subtract each element of K (what I wanted to use the extra dimension for), take the positive part (i.e. max of the result and 0) and sum out the first dimension x to get a y times n matrix.

 K=reshape(K,1,1);
 result = squeeze( sum( max(  bsxfun(@minus,S,K), 0), 1 )  )

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Hi Marius Adom,

If I understood your task correctly, you can use arrayfun() to create each x-y-Matrix and concatenate them using cat():

x = 4;
y = 3;
v = [1 2 3 4 5];
cOut = arrayfun(@(dIn,nInd) ones(x,y) .* dIn, v, 1:length(v), 'UniformOutput',false);
dOut = cat(3,cOut{:});

Kind regards,

Robert

Best Answer

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