The number of cluster. If NULL (the default), it is set to the largest drop
in aggregation height.
method
Character string defining the clustering method.
engine
Which implementation builds the hierarchy: hclust (the
default) or agnes. They give the same hierarchy -- same heights, to
machine precision, and the same cut -- but hclust is far faster on a large dataset
(0.3 s against 30 s on 3000 observations). Use "agnes" for the linkages it alone
provides, or to compare the two.
graph
A logical indicating whether or not a graphic should be plotted (the
aggregation heights used to choose k, when k is not given).