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1 | /* | |
2 | * Copyright (c) 2003, the JUNG Project and the Regents of the University | |
3 | * of California | |
4 | * All rights reserved. | |
5 | * | |
6 | * This software is open-source under the BSD license; see either | |
7 | * "license.txt" or | |
8 | * http://jung.sourceforge.net/license.txt for a description. | |
9 | */ | |
10 | package edu.uci.ics.jung.algorithms.importance; | |
11 | ||
12 | import java.util.Iterator; | |
13 | ||
14 | import edu.uci.ics.jung.graph.UndirectedGraph; | |
15 | import edu.uci.ics.jung.graph.Vertex; | |
16 | ||
17 | /** | |
18 | * Computes betweenness centrality for each vertex in the graph. The betweenness values in this case | |
19 | * are based on random walks, measuring the expected number of times a node is traversed by a random walk | |
20 | * averaged over all pairs of nodes. The result is that each vertex has a UserData element of type | |
21 | * MutableDouble whose key is 'centrality.RandomWalkBetweennessCentrality' | |
22 | * | |
23 | * A simple example of usage is: <br> | |
24 | * RandomWalkBetweenness ranker = new RandomWalkBetweenness(someGraph); <br> | |
25 | * ranker.evaluate(); <br> | |
26 | * ranker.printRankings(); <p> | |
27 | * | |
28 | * Running time is: O((m+n)*n^2). | |
29 | * @see "Mark Newman: A measure of betweenness centrality based on random walks, 2002." | |
30 | ||
31 | * @author Scott White | |
32 | */ | |
33 | public class RandomWalkBetweenness extends RandomWalkSTBetweenness { | |
34 | ||
35 | public static final String CENTRALITY = "centrality.RandomWalkBetweennessCentrality"; | |
36 | ||
37 | /** | |
38 | * Constructor which initializes the algorithm | |
39 | * @param g the graph whose nodes are to be analyzed | |
40 | */ | |
41 | public RandomWalkBetweenness(UndirectedGraph g) { | |
42 | 1 | super(g,null,null); |
43 | 1 | } |
44 | ||
45 | protected void computeBetweenness() { | |
46 | 1 | setUp(); |
47 | ||
48 | 1 | int numVertices = getGraph().numVertices(); |
49 | 1 | double normalizingConstant = numVertices*(numVertices-1)/2.0; |
50 | ||
51 | 1 | for (Iterator iIt = getGraph().getVertices().iterator();iIt.hasNext();) { |
52 | 11 | Vertex ithVertex = (Vertex) iIt.next(); |
53 | ||
54 | 11 | double ithBetweenness = 0; |
55 | 132 | for (int t=0;t<numVertices;t++) { |
56 | 726 | for (int s=0;s<t;s++) { |
57 | 605 | Vertex sthVertex = (Vertex) getIndexer().getVertex(s); |
58 | 605 | Vertex tthVertex = (Vertex) getIndexer().getVertex(t); |
59 | 605 | ithBetweenness += computeSTBetweenness(ithVertex,sthVertex, tthVertex); |
60 | } | |
61 | } | |
62 | 11 | setRankScore(ithVertex,ithBetweenness/normalizingConstant); |
63 | } | |
64 | 1 | } |
65 | ||
66 | ||
67 | ||
68 | /** | |
69 | * the user datum key used to store the rank scores | |
70 | * @return the key | |
71 | */ | |
72 | public String getRankScoreKey() { | |
73 | 38 | return CENTRALITY; |
74 | } | |
75 | ||
76 | protected double evaluateIteration() { | |
77 | 1 | computeBetweenness(); |
78 | 1 | return 0; |
79 | } | |
80 | } |
this report was generated by version 1.0.5 of jcoverage. |
copyright © 2003, jcoverage ltd. all rights reserved. |