wolffd@0: function U = mk_undirected(G)
wolffd@0: 
wolffd@0: [nr nc] = size(G);
wolffd@0: U = G;
wolffd@0: for i=1:nr
wolffd@0:   for j=1:nc
wolffd@0:     if U(i,j)==1
wolffd@0:       U(j,i) = 1;
wolffd@0:     end
wolffd@0:   end
wolffd@0: end