function V = unvecreal(v)% function V = unvecreal(v)%% form matrix V from col vector v, where V has n columns.% This version: make use of symmetry (inverse of vecreal() )[m,N] = size(v);n = sqrt(m);m = m/n;Y = zeros(m,n);for i=1:m,   Y(i,:) = v((i-1)*m+1:i*m)';endY1 = triu(Y,1);Y2 = tril(Y,-1);Yd = diag(Y)/sqrt(2);Y1 = Y1 + diag(Yd);V = (Y1 + Y1')/sqrt(2) + sqrt(-1)*(Y2' - Y2)/sqrt(2);