summaryrefslogtreecommitdiff
path: root/src/de/lmu/ifi/dbs/elki/distance/distancefunction/probabilistic/JensenShannonDivergenceDistanceFunction.java
blob: d7692dcca9136b113d7fb68f8a74b479605d481e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
package de.lmu.ifi.dbs.elki.distance.distancefunction.probabilistic;

/*
 This file is part of ELKI:
 Environment for Developing KDD-Applications Supported by Index-Structures

 Copyright (C) 2011
 Ludwig-Maximilians-Universität München
 Lehr- und Forschungseinheit für Datenbanksysteme
 ELKI Development Team

 This program is free software: you can redistribute it and/or modify
 it under the terms of the GNU Affero General Public License as published by
 the Free Software Foundation, either version 3 of the License, or
 (at your option) any later version.

 This program is distributed in the hope that it will be useful,
 but WITHOUT ANY WARRANTY; without even the implied warranty of
 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU Affero General Public License for more details.

 You should have received a copy of the GNU Affero General Public License
 along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

import de.lmu.ifi.dbs.elki.data.NumberVector;
import de.lmu.ifi.dbs.elki.utilities.optionhandling.AbstractParameterizer;

/**
 * Jensen-Shannon Divergence is essentially the same as Jeffrey divergence, only
 * scaled by half.
 * 
 * @author Erich Schubert
 */
public class JensenShannonDivergenceDistanceFunction extends JeffreyDivergenceDistanceFunction {
  /**
   * Static instance. Use this!
   */
  public static final JensenShannonDivergenceDistanceFunction STATIC = new JensenShannonDivergenceDistanceFunction();

  /**
   * Constructor for the Jensen-Shannon divergence.
   *
   * @deprecated Use static instance!
   */
  @Deprecated
  public JensenShannonDivergenceDistanceFunction() {
    super();
  }

  @Override
  public double doubleDistance(NumberVector<?> v1, NumberVector<?> v2) {
    return .5 * super.doubleDistance(v1, v2);
  }

  @Override
  public String toString() {
    return "JensenShannonDivergenceDistance";
  }

  /**
   * Parameterization class, using the static instance.
   * 
   * @author Erich Schubert
   * 
   * @apiviz.exclude
   */
  public static class Parameterizer extends AbstractParameterizer {
    @Override
    protected JensenShannonDivergenceDistanceFunction makeInstance() {
      return STATIC;
    }
  }
}