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Cluster Analysis
So far, the Gifi cluster analysis is in the 1989 Psychometrika
paper by Van Buuren and Heiser on GROUPALS. GROUPALS also
exists as a computer program. Although GROUPALS is undoubtedly
the most straightforward extension of HOMALS, there are other
forms of cluster analysis that have not been studied. Basically,
every cluster method based on a loss function can be extended
in the usual way with OS, by also optimizing over transformations.
It is interesting to generalize the hierarchical cluster methods
(and to study the relationships between them and CA, as the
Benzecrists have done).
Under this topic we can also discuss the MDS-type generalizations
of PCA in De Leeuw and Meulman, and in the thesis of Meulman.
Moreover there are relationships with the general concept of
dimensionality.
