Self loop

[gitbestsou]

Can there be more than one edge between two nodes in this example?

[ubi15]

There is no limit on the number of edges between two nodes. However, they will be plotted equally so that they will be indistinguishable. If you want to implement it consider adding a check on the number of edges a control on the number of edges between two nodes Then cycle over the edges and for each of them pass to xy_edge(i,j,c,r) an optional offset argument like xy_edge(i,j,c,r, offset=.0): that you pass to the Vertex(p1,p2,c, offset=0) and add to m+direttrice*(offset + min_d+max_d*(1.-distanza(m,c)/distanza(c,p1))).

Hope this help.