InDisc: An R Package for Assessing Person and Item Discrimination in Typical-Response Measures.

InDisc is an R Package that implements procedures for estimating and fitting unidimensional Item Response Theory (IRT) Dual Models (DMs). DMs are intended for personality and attitude measures and are, essentially, extended standard IRT models with an extra person parameter that models the discriminating power of the individual. The package consists of a main function, which calls subfunctions for fitting binary, graded, and continuous responses. The program, a detailed user's guide, and an empirical example are available at no cost to the interested practitioner.