On Mon, 2011-06-20 at 13:38 +0200, Dominik P.H. Kalisch wrote: > Hi, > > I would like to cluster a dataset with the ward algorithm.
I'm assuming that this refers to the agglomerative partitioning method [1]. That is, the number of clusters is selected according to the data partition that is sequentially optimal with respect to an `objective function'. In order to apply the elbow criterion, it should be possible to optimize over subsets of all possible data partitions where the number of clusters is fixed. Although the Ward method yields a sequence of data partitions with decreasing cluster sizes, there is no guarantee that _any_ of these partitions are optimal (except sequentially, of course). To apply the elbow method post hoc seems dubious, but maybe no more so than the Ward method itself. There are clustering methods that optimize the data partition (w.r.t a likelihood/posterior) with a fixed number of clusters, for instance, those based on finite mixture models. The elbow principle and method seem more valid in this context. See the R package 'mclust', and the CRAN task view for cluster analysis: http://cran.r-project.org/web/views/Cluster.html > That works fine. But I can't find a method to plot the structure chart > to estimate the "elbow crterion" for the number of clusters. > Can someone tell me how I can do it? > > Thanks for your help. > Dominik > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. [1] Ward, J. H. (1963), “Hierarchical Grouping to Optimize an Objective Function,” Journal of the American Statistical Association, 58, 236–244. -- Matthew S. Shotwell Assistant Professor, Department of Biostatistics School of Medicine, Vanderbilt University 1161 21st Ave. S2323 MCN Office CC2102L Nashville, TN 37232-2158 ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
