How Factor Analysis Can Be Used in Classification

This is a methodological study that suggests a taxometric technique for objective classification of yeasts. It makes use of the minres method of factor analysis and groups strains of yeast according to their factor profiles. The similarities are judged in the higher-dimensional space determined by the factor analysis, but otherwise rely on the simple concept of "most like" or "neighbor." The proposed techniques are illustrated by means of an example involving 110 strains of yeast with measurements on 30 variables. An analysis in terms of six factors is obtained and the six-dimensional factor profiles for the strains are the basis for determining neighbors and classifying the strains into groups. The automatic procedure leads to 32 groups. Then, by applying the procedures again, only eight second-order groups, or clusters, emerge.