de.lmu.ifi.dbs.elki.algorithm.clustering.hierarchical.linkage

Class MedianLinkage

java.lang.Object

de.lmu.ifi.dbs.elki.algorithm.clustering.hierarchical.linkage.MedianLinkage

All Implemented Interfaces:

Linkage

@Reference(authors="J. C. Gower",
           title="A comparison of some methods of cluster analysis",
           booktitle="Biometrics (1967)",
           url="https://doi.org/10.2307/2528417",
           bibkey="doi:10.2307/2528417")
 @Alias(value={"wpgmc","WPGMC","weighted-centroid","de.lmu.ifi.dbs.elki.algorithm.clustering.hierarchical.MedianLinkageMethod"})
public class MedianLinkage
extends java.lang.Object
implements Linkage

Median-linkage — weighted pair group method using centroids (WPGMC).

Similar to WeightedAverageLinkage (WPGMA), the weight of points in this method decreases with the depth of the tree. This yields to difficult to understand semantics of the result, as it does not yield the distance of medians. The method is best defined recursively: \[d_{\text{WPGMC}}(A\cup B,C):=\tfrac{1}{2}d(A,C)+\tfrac{1}{2}d(B,C) -\tfrac{1}{4}d(A,B)\]

Reference:

J. C. Gower
A comparison of some methods of cluster analysis
Biometrics (1967): 623-637.

Since:

0.6.0

Author:

Erich Schubert

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	MedianLinkage.Parameterizer Class parameterizer.

Field Summary

Fields

Modifier and Type	Field and Description
static MedianLinkage	STATIC Static instance of class.

Constructor Summary

Constructors

Constructor and Description
MedianLinkage() Deprecated. use the static instance STATIC instead.

Method Summary

Modifier and Type	Method and Description
double	combine(int sizex, double dx, int sizey, double dy, int sizej, double dxy) Compute combined linkage for two clusters.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Methods inherited from interface de.lmu.ifi.dbs.elki.algorithm.clustering.hierarchical.linkage.Linkage

initial, restore

Field Detail

STATIC

public static final MedianLinkage STATIC

Static instance of class.

Constructor Detail

MedianLinkage

@Deprecated
public MedianLinkage()

Deprecated. use the static instance STATIC instead.

Constructor.

Method Detail

combine

public double combine(int sizex,
                      double dx,
                      int sizey,
                      double dy,
                      int sizej,
                      double dxy)

Description copied from interface: Linkage

Compute combined linkage for two clusters.

Specified by:

combine in interface Linkage

Parameters:

sizex - Size of first cluster x before merging

dx - Distance of cluster x to j before merging

sizey - Size of second cluster y before merging

dy - Distance of cluster y to j before merging

sizej - Size of candidate cluster j

dxy - Distance between clusters x and y before merging

Returns:

Combined distance