How to rewrite matrix ‘Y’ as matrix ‘A’?

Let ‘Y’ be a matrix of ‘N’ rows and ‘T’ columns. How to rewrite matrix ‘Y’ as matrix ‘A’? Where matrix ‘A’ is having ‘N*(T-2)’ rows and ‘((T-1)*(T-2))/2’ columns.

Answer 1

[Thorsten]

You can also use for-loops:

 for j = 1:size(Y, 1)
   for i = 1:size(Y,2)
     A(i+(j-1)*size(Y,2),(1:i)+sum(1:i-1)) = Y(j,1:i);
   end
 end

Answer 2

[Andrei Bobrov]

EDIT

[m,n] = size(Y);
nn = 1:n;
i0 = triu(nn'*ones(1,n));
i0 = i0(i0 > 0).';
ic = mat2cell(ones(size(i0)),1,nn);
A = repmat(blkdiag(ic{:}),m,1);
[ii,jj] = ndgrid(1:m,i0);
A(A > 0) = Y(sub2ind(size(Y),ii,jj));

[SAGAR MATUR]

I am getting this error: "??? Error using ==> sub2ind at 52 The subscripts vectors must all be of the same size." in MATLAB version R2011a

[Andrei Bobrov]

Corrected code