How to copy all elements diagonally below the diagonal in Matlab?

Question

I want to copy all the elements above the diagonal (not diagonal) under the diagonal without using any cycle or at minimal cost. So, after copying, the matrix will become a symmetric matrix:
i.e. for all i, j: A(i,j)=A(j,i).

Thank.

Answer 1

Use the command triu:

>> symMat = triu( A, 0 ) + triu( A, 1 ).';

This command will leave the diagonal Aunchanged.