— Function File: y = linkage (x)
— Function File: y = linkage (x, method)

Return clusters generated from a distance vector created by the pdist function.

Methods can be:

‘"single" (default)’

Shortest distance between two clusters (aka a minimum spanning tree)

‘"complete"’

Furthest distance between two clusters

‘"average"’

Unweighted average distance (aka group average)

‘"weighted"’

Weighted average distance

‘"centroid"’

Centroid distance (not implemented)

‘"median"’

Weighted center of mass distance

‘"ward"’

Inner squared distance (minimum variance)

x is an ((m-1)*(m/2) x 1) distance vector as generated by pdist, and the output, y is an ((m - 1) x 3) vector defined with columns where the first and second columns are the cluster numbers of the two sub-clusters in the cluster, and the third column is the distance between those sub-clusters. The sub-clusters are numbered where 1 to m are the input elements, and m+1 to the end are subsequently defined clusters.

See also: cluster, pdist