third-party/net.sf.jung2/src/main/java/edu/uci/ics/jung/algorithms/scoring/util/UniformDegreeWeight.java

   1 /**
   2  * Copyright (c) 2008, 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  * Created on Jul 14, 2008
  10  *
  11  */
  12 package edu.uci.ics.jung.algorithms.scoring.util;
  13
  14 import org.apache.commons.collections15.Transformer;
  15
  16 import edu.uci.ics.jung.graph.Hypergraph;
  17 import edu.uci.ics.jung.graph.util.EdgeType;
  18
  19 /**
  20  * An edge weight function that assigns weights as uniform
  21  * transition probabilities.
  22  * For undirected edges, returns 1/degree(v) (where 'v' is the
  23  * vertex in the VEPair.
  24  * For directed edges, returns 1/outdegree(source(e)) (where 'e'
  25  * is the edge in the VEPair).
  26  * Throws an <code>IllegalArgumentException</code> if the input
  27  * edge is neither EdgeType.UNDIRECTED nor EdgeType.DIRECTED.
  28  *
  29  */
  30 public class UniformDegreeWeight<V, E> implements
  31                 Transformer<VEPair<V, E>, Double>
  32 {
  33     private Hypergraph<V, E> graph;
  34
  35     /**
  36      * Creates an instance for the specified graph.
  37      */
  38     public UniformDegreeWeight(Hypergraph<V, E> graph)
  39     {
  40         this.graph = graph;
  41     }
  42
  43         /**
  44          * @see org.apache.commons.collections15.Transformer#transform(java.lang.Object)
  45          */
  46         public Double transform(VEPair<V, E> ve_pair)
  47         {
  48                 E e = ve_pair.getE();
  49                 V v = ve_pair.getV();
  50                 EdgeType edge_type = graph.getEdgeType(e);
  51                 if (edge_type == EdgeType.UNDIRECTED)
  52                         return 1.0 / graph.degree(v);
  53                 if (edge_type == EdgeType.DIRECTED)
  54                         return 1.0 / graph.outDegree(graph.getSource(e));
  55                 throw new IllegalArgumentException("can't handle edge type: " + edge_type);
  56         }
  57
  58 }