This is to announce the new R-package ?ordinal? that implements
cumulative link (mixed) models for ordinal (ordered categorical) data
(http://www.cran.r-project.org/package=ordinal/).
The main features are:
- scale (multiplicative) as well as location (additive) effects
- nominal effects for a subset of the predictors (denoted partial
proportional odds when the link is the logistic)
- structured thresholds, e.g. assuming symmetry or equidistant thresholds
- random effects via the Laplace approximation and adaptive
Gauss-Hermite quadrature in the location-part of the model.
- a range of standard link functions
- flexible link functions where an extra link function-parameter
bridges the log-log, probit and c-loglog links (log-gamma), and
cloglog and logistic links (Aranda-Ordaz)
- a suite of optimizers including an efficient Newton scheme.
- works for binomial observations (a special case of ordinal data).
- a suite of methods including anova, addterm, dropterm, profile,
confint, plot.profile, predict, in addition to the standard print and
summary methods.
- an important special case is the proportional odds model (with
random effects).
- a range of examples illustrates how to use the functions.
Future additions will include:
- more general random effect structures: multiple (crossed and nested)
and vector-valued random effects.
- profile methods for variance parameters in mixed effect models.
- helpful package vignettes.
- implementation of core functions in C.
Comments, critique, suggestions, wishes and contributions are always
highly appreciated.
Kind regards
Rune
--
Rune Haubo Bojesen Christensen
PhD student, M.Sc. Eng.
Phone: (+45) 45 25 33 63
Mail: rhbc at imm.dtu.dk
DTU Informatics, Section for Statistics
Technical University of Denmark, Build. 305, Room 122,
DK-2800 Kgs. Lyngby, Denmark
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