2494	 A Computer Generated Aid for Cluster Analysis	 A computer generated graphic method which can be used in conjunction with any hierarchical scheme of cluster analysis is described and illustrated. The graphic principle used is the representation of the elements of a data matrix of similarities or dissimilarities by computer printed symbols of character overstrikes of various shades of darkness where a dark symbol corresponds to a small dissimilarity. The plots applied to a data matrix before clustering and to the rearranged matrix after clustering show at a glance whether clustering brought forth any distinctive clusters. A well-known set of data consisting of the correlations of psychological tests is used to illustrate the comparison of groupings by four methods of factor analysis and two methods of cluster analysis. computer graphics cluster analysis numerical taxonomy hierarchical clustering factor analysis
