Data reduction for graphical and other purposes

Reducing a dataset to another dataset containing summary or other statistics is an old problem, much addressed in Stata by oacial commands such as collapse, contract, or statsby and by various community-contributed commands. Often, an underlying principle is that a valuable command should do one thing well so that a reduction command is just one step in a sequence that includes other analyses. This presentation focuses on a bundle of new commands recently posted on SSC: cisets, momentsets, pctilesets, and lmomentsets. They have much in common, including support for obtaining results for multiple variables and for distinct groups of a single variable. Typically, the next stage is some graphical representation, such as a customized variation on existing designs. Examples of their use will be coupled with ruminations on the tradeoffs in command design for programmers and users alike, between versatility and simplicity. As in the rest of life, sometimes programmers need to step back before they can move forward in a better direction.