split_edge - splits an edge by inserting a node
split_edge returns the graph g1, the edge from node number i to node number j being splitted: a new node is created and located at the middle point between the 2 previous nodes. This new node is linked with the 2 nodes i and j. If name is given, it is the name of the new node, otherwise the number of nodes plus 1 is taken as the name of the new node.
ta=[1 1 2 2 2 3 4 5 5 7 8 8 9 10 10 10 10 10 11 12 13 13 13 14 15 16 16 17 17];
he=[2 10 3 5 7 4 2 4 6 8 6 9 7 7 11 13 13 15 12 13 9 10 14 11 16 1 17 14 15];
g=make_graph('foo',1,17,ta,he);
g('node_x')=[283 163 63 57 164 164 273 271 339 384 504 513 439 623 631 757 642];
g('node_y')=[59 133 223 318 227 319 221 324 432 141 209 319 428 443 187 151 301];
show_graph(g);
gt=split_edge(1,2,g);
show_graph(gt,'new');