BetweenessCentrality for directed graphs

[<schoellhorn AT ifm.uni-mannheim.de>]

Hi,

I'd like to compute the BetweenessCentrality for a directed Graph. But when
changing the example on
http://graphstream-project.org/doc/Algorithms/Betweenness-Centrality/ to a
directed graph the algorithm stop. with a NullpointerException. 

As far as I am aware the BC can be computed for directed Graphs as well. Is it
possible with GraphStream? Do you have any proposals how to achieve that?



Tino

P.S: Example-Code:

Graph graph = new SingleGraph("Betweenness Test");

                Node A = graph.addNode("A");
                Node B = graph.addNode("B");
                Node E = graph.addNode("E");
                Node C = graph.addNode("C");
                Node D = graph.addNode("D");
        
                graph.addEdge("AB", "A", "B", true);
                graph.addEdge("BE", "B", "E", true);
                graph.addEdge("BC", "B", "C", true);
                graph.addEdge("ED", "E", "D", true);
                graph.addEdge("CD", "C", "D", true);
                graph.addEdge("AE", "A", "E", true);
        
                BetweennessCentrality bcb = new BetweennessCentrality();
                bcb.setWeightAttributeName("weight");
                bcb.setWeight(A, B, 1);
                bcb.setWeight(B, E, 6);
                bcb.setWeight(B, C, 5);
                bcb.setWeight(E, D, 2);
                bcb.setWeight(C, D, 3);
                bcb.setWeight(A, E, 4);
                bcb.init(graph);
                bcb.compute();
        
                System.out.println("A="+ A.getAttribute("Cb"));
                System.out.println("B="+ B.getAttribute("Cb"));
                System.out.println("C="+ C.getAttribute("Cb"));
                System.out.println("D="+ D.getAttribute("Cb"));
                System.out.println("E="+ E.getAttribute("Cb"));