A technique, proposed by Hartley in a 1935 paper, that results in the display of data from a contingency table in a scatter diagram that includes points representing row categories and points representing column categories. If row points are positioned near each other in the diagram then this implies that the patterns of counts along those rows are very similar. The same applies for groups of column points. If a row point and a column point are positioned close to one another then this implies a positive association between the two. The calculations involved resemble those for principal components analysis.