Question

How do I create the following graph with the graphviz c-library:

digraph G {
    {rank=same; n1, n2}
    n1 -> n2 -> n3;
}

The following lines are clear:

g = agopen("G", AGFLAG_DIRECTED);
agnode(g, "n1");
agnode(g, "n2");
agnode(g, "n3");
agedge(g, "n1", "n2");
agedge(g, "n2", "n3");

How do I rank n1 and n2?

Answer 1

I’ve found a solution. The braces gave me the hint.

{rank=same; n1, n2}

It must be a subgraph. So the following lines will do the trick:

Agraph_t *sub = agsubg(g, "");
agsafeset(sub, "rank", "same", "");