R package. A number of routines for personality, psychometrics and experimental psychology. Functions are primarily for scale construction using factor analysis, cluster analysis and reliability analysis, although others provide basic descriptive statistics. Item Response Theory is done using factor analysis of tetrachoric and polychoric correlations. Functions for simulating particular item and test structures are included. Several functions serve as a useful front end for structural equation modeling. Graphical displays of path diagrams, factor analysis and structural equation models are created using basic graphics. Some of the functions are written to support a book on psychometrics as well as publications in personality research. For more information, see the personality-project.org/r webpage. Item response theory (IRT) is a psychometric approach which assumes that the probability of a certain response is a direct function of an underlying trait or traits. Various functions have been proposed to model this relationship, and the different calibration packages reflect this. Several software packages have been developed for additional analysis such as equating; they are listed in the next section. BILOG-MG is a software program for IRT analysis of dichotomous (correct/incorrect) data, including fit and differential item functioning. It is commercial, and only available from Scientific Software International or Assessment Systems Corporation.  dexter, first published February 2017, is an R package intended as a robust and fairly comprehensive system for managing and analyzing test data organized in booklets. The package includes facilities for importing and managing test data, assessing and improving the quality of data through basic test-and-item analysis, fitting an IRT model, and computing various estimates of ability. Many psychometric methods not found elsewhere are provided, such as Haberman’s (2007) interaction model generalized for polytomous items, efficient generation of plausible values or scores, new methods for exploratory and confirmatory DIF analysis, support for the 3DC method of standard setting, and many more. The central IRT model is a polytomous generalization of the extended marginal Rasch model. Estimation is by CML or Bayesian techniques. There are two companion packages: dextergui, first published June 2018, and providing an easy graphical interface to the most widely used functions in dexter; and dexterMST, first published July 2018, for managing and analyzing data from multi-stage test designs. All packages are extensively documented both for the beginner as for the professional (see also the blog). Facets is a software program for Rasch analysis of rater- or judge-intermediated data, such as essay grades, diving competitions, satisfaction surveys and quality-of-life data.