Dynamic Path Diagrams E. F. Haghish Center for Medical Biometry and Medical Informatics (IMBI) University of Freiburg, Germany and Department of Mathematics and Computer Science University of Southern Denmark
[email protected] Abstract. Diagrams are frequently used in data analysis and visualization. Stata provides an SEM builder interface to develop SEM path diagrams, execute the analysis, and export the analysis diagram to an image file. However, this process is manual and cannot be reproduced in an automated analy- sis. This article introduces the diagram package which renders \DOT" (Graph Descriptive Language) diagrams and exports them to a variety of formats including PDF, PNG, JPEG, GIF, and BMP with adjustable resolution within Stata. Rendering diagrams from a markup language provides the possibility to create diagrams for different purposes, which increases their applications beyond building SEM models. The article discusses potential applications of the package in data analysis and vi- sualization and provides several examples for generating dynamic path diagrams, producing path diagrams from data sets, and visualizing func- tion call for Stata ado-programs. Keywords: Graphviz, graphics, DOT, diagram, reproducible research, vi- sualization, SEM 1 Introduction Evaluating relationship among variables is one of the primary concepts in statis- tics. In order to represent and visualize multivariate analytic models, often path diagrams are used, where arrows point out the relationship between vari- ables. The relationship is visualized using a one-headed arrow indicating one variable's direct effect on the other, whereas two-headed arrow indicating un- analyzed correlation. The residual variance is shown by arrows not originating from a variable (Mitchell 1992; Li et al.