Whenevern objects are characterized by a matrix of pairwise dissimilarities, they may be clustered by any of a number of sequential, agglomerative, hierarchical, nonoverlapping (sahn) clusteringmethods. These sahn cl...
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Whenevern objects are characterized by a matrix of pairwise dissimilarities, they may be clustered by any of a number of sequential, agglomerative, hierarchical, nonoverlapping (sahn) clusteringmethods. These sahn clustering methods are defined by a paradigmatic algorithm that usually requires 0(n 3) time, in the worst case, to cluster the objects. An improved algorithm (Anderberg 1973), while still requiring 0(n 3) worst-case time, can reasonably be expected to exhibit 0(n 2) expected behavior. By contrast, we describe a sahnclustering algorithm that requires 0(n 2 logn) time in the worst case. When sahn clustering methods exhibit reasonable space distortion properties, further improvements are possible. We adapt a sahnclustering algorithm, based on the efficient construction of nearest neighbor chains, to obtain a reasonably general sahnclustering algorithm that requires in the worst case 0(n 2) time and space.
Proportional link linkage (PLL) clusteringmethods are a parametric family of monotone invariant agglomerative hierarchical clusteringmethods. This family includes the single, minimedian, and complete linkage cluster...
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Proportional link linkage (PLL) clusteringmethods are a parametric family of monotone invariant agglomerative hierarchical clusteringmethods. This family includes the single, minimedian, and complete linkage clusteringmethods as special cases;its members are used in psychological and ecological applications. Since the literature on clustering space distortion is oriented to quantitative input data, we adapt its basic concepts to input data with only ordinal significance and analyze the space distortion properties of PLL methods. To enable PLL methods to be used when the number n of objects being clustered is large, we describe an efficient PLL algorithm that operates in O(N2 log n) time and O(n2) space.
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