Talk:Ward's method

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Not minimum variance[edit]

The incorrect label for Ward as "minimim variance" method is widely spread. But in fact this method is "minimum increase of sum-of-squares (of errors)", which is not minimum variance. If it were minimum variance, the decision to link a cluster with a singleton point would always be the same as the decision made by centroid linkage method in that case (because assignment a point to the closest centroid guarantees the new cluster with minimal variance), but that is not the case and the two methods - Ward and centroid - can make different decisions in the above situation. See Podany, J. New combinatorial clustering methods // Vegetatio, vol 81, 1989, where on page 67 he's up in arms against incorrect labels for Ward's method. (talk) 13:48, 1 February 2014 (UTC)