Performs complete complete/max/farthest point linkage on the
condensed distance matrix y. See linkage for more
information on the return structure and algorithm.
Parameters :
y :ndarray
The upper triangular of the distance matrix. The result of
pdist is returned in this form.
Returns :
Z :ndarray
A linkage matrix containing the hierarchical clustering. See
the linkage function documentation for more information
on its structure.