* mat = the original -vectorized by vech_gauss- matrix
DESCRIPTION
Retrieves from a matrix vectorized by vech_gauss the original matrix. Note that since vech in gauss does not work as vech in scilab, xpnd1 is not strictly equivalent to invvech1.
EXAMPLE
v=1:5;mat=v'*v;vh=vech_gauss(mat);matr=xpnd1(vh,5);matr-mat// mat is a (5 x 5) symmetric matrix. vh is the corresponding (15 x 1) vectorisation. You can check that mat and matr are the same.