New Kinds of Graphical Representation in Clustering
Edwin Diday · COMPSTAT · 1986
Having chosen a dissimilarity index, hierarchical clustering is one of the most popular techniques used to represent clusters: in fact, the fit between the graphical representation of hierarchies (i.e. dendrograms) and the data is very good only when the two following conditions are satisfied. This paper is devoted to new kinds of graphical representation when those conditions are not satisfied. When the first condition is not satisfied at all, we introduce a complementary notion of ultrametric called “ultramine”. When the second condition is not satisfied at all, a new dissimilarity index called “anti-pyramidal” which is an extension of ultramine is introduced. Graphical representations of those two notions are given. We give a measure which indicate how much the data are ultrametric or ultramine and order compatible or not for the chosen dissimilarity index. Each one of the new graphical representations sheds new and interesting light on the data.