Showing posts with label Biplots. Show all posts
Showing posts with label Biplots. Show all posts

Tuesday, April 10, 2012

Biplots in Stata

I've been examining qualitative data using biplots, which are readily available in Stata using Ulrich Kohler's excellent package. For example, here is a biplot of a rich data set of poor white men on variables such as drug use and other risk factors:
There are several useful features of biplots: first, they concisely summarize a wealth of information in one graph, including relationships among both cases and variables; second, in line with Tufte's dictum, biplots have a high data-to-ink ratio; third, since cases are not directly modeled, biplots help with integrating qualitative and quantitative data (i.e., cases are not "hidden" by a hyperplane, as in a classical linear regression model); finally, there are absolutely no frequentist statistics to deceive the analyst.