- All Implemented Interfaces:
- AgglomerationMethod
public final class WeightedAverageLinkage
extends Object
implements AgglomerationMethod
The "weighted average", "McQuitty", or
"Weighted Pair-Group Method using Arithmetic averages, or WPGMA)" method.
Average linkage where the sizes of the clusters are assumed to be equal.
This method, similar to "Median", weights small and large clusters equally.
[The data analysis handbook. By Ildiko E. Frank, Roberto Todeschini]
The general form of the Lance-Williams matrix-update formula:
d[(i,j),k] = ai*d[i,k] + aj*d[j,k] + b*d[i,j] + g*|d[i,k]-d[j,k]|
For the "McQuitty" method:
ai = 0.5
aj = 0.5
b = 0
g = 0
Thus:
d[(i,j),k] = 0.5*d[i,k] + 0.5*d[j,k]