Letter | Published:

Nodal Analysis of Associated Populations

Naturevolume 191page202 (1961) | Download Citation



A METHOD of subdividing an associated population the individuals of which are specified by the presence or absence of a number of attributes has been described previously1; the process is ultimately derived from the R-techniques of factor analysis, and the groups of individuals so obtained will be called R-groups. The attributes may similarly be subdivided into Q-groups by the corresponding Q-techniques. There results a 2-way table in which every attribute-individual record is referred to one of each kind of group. The requirement is to extract from this table the most concentrated groups of records, the attribute-individual noda around which the population may be regarded as varying. The problem is essentially that of establishing coincidences between R and Q factors; even in normal factor analysis the coincidences are impaired in the formation of the correlation matrix2,3, and in a subdivision process involving successive correlation matrices the divergence may well be considerable.

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  1. 1

    Williams, W. T., and Lance, G. N., Nature, 182, 1755 (1958).

  2. 2

    Slater, P., Nature, 181, 1225 (1958).

  3. 3

    Cattell, R. B., Factor Analysis, 90 (Harper and Bros., New York, 1952).

  4. 4

    Williams, W. T., and Lambert, J. M., J. Ecol., 47, 83 (1959).

  5. 5

    Williams, W. T., and Lambert, J. M., J. Ecol., 48, 689 (1960).

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  1. Botany Department, University of Southampton

    • W. T. WILLIAMS
    •  & J. M. LAMBERT


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