On Mon, Jun 7, 2010 at 9:05 AM, sidahmed BENABDERRAHMANE <sidahmed.benabderrahm...@loria.fr> wrote: > Dear all, > > I have a problem when using some classification functions (Kmeans, PAM, > FANNY...) with a distance matrix, and i would to understand how it proceeds > for the positioning of centroids after one execution step. > > In fact, in the classical formulation of the algorithm, after each step, to > re-position the center, it calculates the distance between any elements of > the old cluster and its center, or in my case I used a distance matrix , so > I do not understand how the algorithm can recalculates the distance between > the newly generated center and other elements of the cluster knowing that > the new center does not appear in the distance matrix and there is no way to > calculate the distance between him and the elements of a cluster. ? >
In my understading PAM stands for Partitioning Around Medoids. The medoid of a cluster is the object with the smallest mean distance to all other objects in the cluster. In each iteration, all objects are assigned to their nearest medoid, and the medoids are updated if necessary. The distance matrix is never recalculated. Someone please correct me if I'm wrong. Peter ______________________________________________ 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.
