Graphics for ordinal outcomes or predictors

Ordered or ordinal variables, such as opinion grades from Strongly disagree to Strongly agree, are common in many fields and a leading data type in some. Alternatively, orderings may be sought in the data. In archaeology and various environmental sciences, there is a problem of seriation, at its simplest finding the best ordering of rows and columns given a data matrix. For example, the goal may be to place archaeological sites in approximate date order according to which artefacts have been found where. Graphics for such data may appear to range from obvious but limited (draw a bar chart if you must) to more powerful but obscure (enthusiasts for complicated mosaic plots or correspondence analyses need to convince the rest of us). Alternatively, graphics are avoided and the focus is only on tabular model output with estimates, standard errors, P-values and so forth. The need for descriptive or exploratory graphics remains. This presentation surveys various graphics commands by the author, made public through the Stata Journal or SSC, that should not seem too esoteric, principally friendlier and more flexible bar charts and dedicated distribution or quantile plots. Specific commands include tabplot, floatplot, qplot and distplot. Mapping grades to scores and considering frequencies, probabilities or cumulative probabilities on transformed scales are also discussed as simple strategies.