Displaying clinical data relationships using scaled rectangle diagrams.

A method is presented to draw rectangles to represent categorical data relationships. The idea is an adaptation of a scaled Venn diagram. Rectangles are drawn with area proportional to the frequency of categories and the rectangles are positioned to overlap each other so that the areas of overlap are in proportion to the joint frequencies of the characteristics. The diagrams are especially useful to illustrate symptom co-occurrence. Copyright 2001 John Wiley & Sons, Ltd.