How to delete one element of the third dimen in a 4d matrix?

Hi,

i have a 4d Matrix with the size of [i j n k] target size is [i j n-1 k] and i want to delete always the smalest of the n elements. I made it like this:

sz = size(Matrix);
Matrix_neu = zeros(sz - [0 0 1 0]);
[~, I] = min(Matrix,[],3);

for i = 1:sz(1)
    for j = 1:sz(2)
        for k = 1:sz(4)
            temp = true(1,sz(3));
            temp(I(i,j,1,k)) = false;
            Matrix_neu(i,j,:,k) = Matrix(i,j,temp,k);
        end
    end
end

but i think there is a more elegant and faster way isn't it?

Regards Markus

Answer 1

[Matt J]

If you know the minima are uniquely attained, you could do something like this,

 [m,n,p,q]=size(Matrix);
 Matrix = reshape( permute(Matrix,[3,2,1,4]), p,[] );

 idx=bsxfun(@gt, Matrix, min(Matrix,[],1));

 Matrix_neu=ipermute( reshape( Matrix(idx),  [p-1,n,m,q]) ,  [3 2 1 4]);

[Markus]

i think there is a typing error: you wrote:

[3 1 2 4] @ ipermute

and:

[3,2,1,4] @ permute

they must be the same or?

Regards Markus

[Matt J]

Yes, they must both be [3 2 1 4]. I've fixed it.