Speaking Stata: MMXI and all that: Handling Roman numerals within Stata

The problem of handling Roman numerals in Stata is used to illustrate issues arising in the handling of classification codes in character string form and their numeric equivalents. The solutions include Stata programs and Mata func- tions for conversion from numeric to string and from string to numeric. Defining acceptable input and trapping and flagging incorrect or unmanageable inputs are key concerns in good practice. Regular expressions are especially valuable for this problem.