- All Known Implementing Classes:
AverageLinkage
, CentroidLinkage
, CompleteLinkage
, MedianLinkage
, SingleLinkage
, WardLinkage
, WeightedAverageLinkage
public interface AgglomerationMethod
An AgglomerationMethod represents the Lance-Williams dissimilarity update formula
used for hierarchical agglomerative clustering.
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]|
Parameters ai, aj, b, and g are defined differently for different methods:
Method ai aj b g
------------- ------------------ ------------------ ------------------------ -----
Single 0.5 0.5 0 -0.5
Complete 0.5 0.5 0 0.5
Average ci/(ci+cj) cj/(ci+cj) 0 0
Centroid ci/(ci+cj) cj/(ci+cj) -ci*cj/((ci+cj)*(ci+cj)) 0
Median 0.5 0.5 -0.25 0
Ward (ci+ck)/(ci+cj+ck) (cj+ck)/(ci+cj+ck) -ck/(ci+cj+ck) 0
WeightedAverage 0.5 0.5 0 0
(ci, cj, ck are cluster cardinalities)