Graphics and categorical data are odd bedfellows. A pie chart of the frequencies of a categorical variable may be the first statistical technique taught to young children, and there is a very substantial if self-contained literature on biplots and related methods. Yet in between many texts and papers on categorical data make little or no use of graphical methods. Is this because appropriate graphs do not exist, or are they too trivial or too ineffective to be worth attention? I shall discuss various Stata implementations of graphs for categorical data, both familiar and unfamiliar, old and new, including bar and dot charts, cumulative and sliding plots, triangular plots, and tabular plots. Subsidiary themes will include, on the statistical side, support for logit and other appropriate non-linear scales, respect for ordinal structure, smoothers for categorical data and transformations of the simplex; and on the Stata side the strategy and trickery of writing user-written graphics programs as wrappers for the new graphics of Stata 8, aiming both to maximise user choice and to minimise user-programmer effort.
