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A Generalized Sorting Strategy for Computer Classifications

Naturevolume 212page218 (1966) | Download Citation



AGGLOMERATIVE hierarchical methods of computer classification all begin by calculating distance-measures between elements. The hierarchy is then generated by subjecting these measures to a sorting-strategy, which depends essentially on the definition of a distance-measure between groups of elements. In nearest-neighbour sorting, this is defined as the distance between the closest pair of elements, one in each group. Macnaughton-Smith has pointed out that much more intense clustering can be produced by taking the most remote pair of elements (furthest-neighbour sorting). In group-average sorting1 the distance is defined as the mean of all between-group inter-element distances; in centroid sorting it is the distance between group centroids, defined by a conventional Euclidean model. In median2 sorting the distance of a third group from two which have just fused depends on the previous three inter-group distances in the manner of Apollonius's theorem. Although the earlier of these strategies have received some comparative assessment1,3–5 no attempt seems to have been made to generalize them into a single system. As a result, quite different computer strategies have commonly been used, necessitating a separate computer program for each.

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  1. 1

    Sokal, R. R., and Michener, C. D., Univ. Kansas Sci. Bull., 38, 1409 (1958).

  2. 2

    Gower, J. C., Biometrics (in the press).

  3. 3

    Sokal, R. R., and Sneath, P. H. A., Principles of Numerical Taxonomy (Freeman, San Francisco and London, 1963).

  4. 4

    Williams, W. T., and Dale, M. B., Adv. Bot. Res., 2, 35 (1965).

  5. 5

    Williams, W. T., Lambert, J. M., and Lance, G. N., J. Ecol., 54, 427 (1966).

  6. 6

    Lance, G. N., and Williams, W. T., Comp. J., 9, 60 (1966).

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  1. C.S.I.R.O. Computing Research Section, Canberra, A.C.T., Australia

    • G. N. LANCE
    •  & W. T. WILLIAMS


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