% plot list of edges, given as  n by 2 array, with 
% positions given in 2 column array.

function   plot_edge_list(edges,verts)
   for k=1:size(edges,1)
       v1=edges(k,1);
       v2=edges(k,2);
       x1=verts(v1,1);
       y1=verts(v1,2);
       x2=verts(v2,1);
       y2=verts(v2,2);
       plot([x1;x2],[y1;y2],'k','LineWidth',2);
   end % for k

return
