MATLAB: How to recover a square matrix from its upper triangular cell part

cellsymmetric

Hi all,
I'd like to compute the upper triangular part only for a symmetric matrix in a block by block way. After some operations I got this:
K>> tempBlk{:}
ans = 
    [6x6 double]    [6x5 double]    [6x5 double]    [6x5 double]
              []    [5x5 double]    [5x5 double]    [5x5 double]
              []              []    [5x5 double]    [5x5 double]
              []              []              []    [5x5 double]
The cell blocks in the diagonal line here are full, symmetric, and the non-diagonal cell blocks are full, non-symmetric. The entire symmetric matrix result should be 21 by 21, which has the length and width of 6+5+5+5. I'd like to fill the empty cells (these [ ]) with zeros, then use cell2mat to transform it back to scalar matrix, then use triu to take only the upper triangular part.
Any idea of how to do this? Thanks!

Best Answer

There's no reason to fill the [] cells with zeros. You can fill them with anything, since they will eventually be overwritten with zeros by triu. I would therefore do as follows:
idx=cellfun('isempty', yourCellArray);
    C=cellfun(@transpose,yourCellArray.','uni',0);
  yourCellArray(idx)=C(idx);
result = triu(cell2mat(yourCellArray))
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