calinski is a Stata add-on that calculates the Calinski-Harabasz pseudo-F for stopping
rules in cluster analysis, from the pairwise distance matrix.
This is widely used to determine the optimum number of clusters.
Stata's default cluster stop does the same calculation on the
basis of the original variables, but cannot operate on the
distance matrix. calinski is thus useful when the original
variables are not available, or when the distances are created
other than as squared Euclidean distances between variables
(as is the case for instance with sequence analysis).