Scilab function

graph_union - union of two graphs

### Calling Sequence

  `g2 = graph_union(g,g1)`

### Parameters

- `g` : graph list
- `g1` : graph list
- `g2` : graph list of the new graph

### Description

`graph_union` creates a new graph `g2`. The node set of `g2` is the union (in the usual sense) of the node sets of `g` and `g1`. `g2` has an edge for each edge of `g` and an edge for each edge of `g1`. The edges of `g` and `g1` having the same endpoints are kept and in this case `g2` has multiple edges.

### Examples

    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];
    g('edge_color')=modulo([1:(edge_number(g))],15)+1;
    g('node_diam')=[1:(g('node_number'))]+20;
    g('node_name')=['A' 'B' 'C' 'D' 'E' 'F' 'G' 'H' 'I' 'J' 'K' 'L' 'M' 'N' 'O' 'P' 'Q'];
    w=show_graph(g);
    v=[7 8 9 10 11 12 13];
    show_nodes(v);
    g1=subgraph(v,'nodes',g);
    show_graph(g1,'new');
    v=[1 2 5 6 7 8 9 10];
    netwindow(w);
    show_nodes(v);
    g2=subgraph(v,'nodes',g);
    show_graph(g2,'new');
    g=graph_union(g1,g2);
    show_graph(g,'new');

### See Also

`supernode` `subgraph`