make_graph - makes a graph list
make_graph makes a graph list according to its arguments which are respectively the name of the graph, a flag for directed or undirected, the number of nodes and the row vectors tail and head. These are the minimal data needed for a graph.
If n is a positive number, graph g has n nodes; this number must be greater than or equal to max(max(tail),max(head)). If it is greater than this number,graph g has isolated nodes. The nodes names are taken as the nodes numbers.
If n is equal to 0, graph g has no isolated node and the number of nodes is computed from tail and head. The nodes names are taken from the numbers in tail and head.
// creating a directed graph with 3 nodes and 4 arcs. g=make_graph('foo',1,3,[1,2,3,1],[2,3,1,3]); // creating a directed graph with 13 nodes and 14 arcs. ta=[1 1 2 7 8 9 10 10 10 10 11 12 13 13]; he=[2 10 7 8 9 7 7 11 13 13 12 13 9 10]; g=make_graph('foo',1,13,ta,he); g('node_x')=[120 98 87 188 439 698 226 127 342 467 711 779 477]; g('node_y')=[ 21 184 308 426 435 428 129 360 435 55 109 320 321]; show_graph(g) // creating same graph without isolated node and 14 arcs. g=make_graph('foo',1,0,ta,he); g('node_x')=[120 98 226 127 342 467 711 779 477]; g('node_y')=[ 21 184 129 360 435 55 109 320 321]; show_graph(g,'new')