plot.partition(x, ...)
x
|
an object of class "partition" , e.g. created by the functions pam ,
clara , and fanny .
Graphical parameters (see par ) may also
be supplied as arguments to this function.
|
k
(the number of
clusters). Finally, choose the value of k
with the largest overall
average silhouette width.
The silhouette width is computed as follows: Put a(i) = average dissimilarity between i and all other points of the cluster to which i belongs. For all clusters C, put d(i,C) = average dissimilarity of i to all objects of C. The smallest of these d(i,C) is denoted as b(i), and can be seen as the dissimilarity between i and its neighbor cluster. Finally, put s(i) = ( b(i) - a(i) ) / max( a(i), b(i) ). The overall average silhouette width is then simply the average of s(i) over all objects i.
Rousseeuw, P.J. (1987). Silhouettes: A graphical aid to the interpretation and validation of cluster analysis. J. Comput. Appl. Math., 20, 53-65.
partition.object
, pam
, pam.object
, clara
, clara.object
, 'fanny
,
fanny.object
, par
.
#generate 25 objects, divided into 2 clusters. x <- rbind(cbind(rnorm(10,0,0.5),rnorm(10,0,0.5)), cbind(rnorm(15,5,0.5),rnorm(15,5,0.5))) plot(pam(x, 2))