So Raul, according to what you said On Wed, Mar 21, 2012 at 9:25 AM, Raul Miller <rauldmil...@gmail.com> wrote: ... > I should also note that a "directed acyclic graph" means that the data > can be sorted such that the connection matrix is lower-triangular.
I think that answers my question below about whether my example is a DAG - if I swap the labels for nodes 3 & 5, the adjacency matrix would be triangular, though upper-triangular which I assume is conceptually the same (because we can convert one to the other by swapping node "n" with "5-n"). NB.* egDAG: example picture of a directed acyclic graph with the NB. characters "V>" (and, potentially, "^<") representing directional NB. arrowheads; "V>" together means a split both down and to the right. egDAG=: 0 : 0 0->2->5 | | | V V>--->4 | V 1 | V 3 ) NB. Is this a DAG if you can reach "4" by two different paths? NB. The picture above corresponds to this adjacency matrix representation. amDAGeg=: ".&><;._2 ] 0 : 0 0 1 1 0 0 0 0 0 0 1 0 0 0 0 0 0 0 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 1 0 ) NB. Vertex Array representation of same graph as above. vaDAGeg=: ,&.>(1 2);(3);(5);(i.0);(i.0);<4 NB. A (nodes);(edges) representation of the above DAG. neDAGeg=: (0 1 2 3 4 5);<|:0 1,0 2,1 3,2 5,:5 4 -- Devon McCormick, CFA ^me^ at acm. org is my preferred e-mail ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
