poly.mod-class function

Class "poly.mod"

The formal S4 class for poly.mod. This class characterizes the models and associated items for a set of item parameters. class

Objects from the Class

Objects can be created by calls of the form new("poly.mod", ...), but this is not encouraged. Use the function as.poly.mod instead.

Slots

• model:: character vector identifying all the models associated with the corresponding set of item parameters. The only acceptable models are drm, gpcm, grm, mcm, and nrm. See below for more details.
• items:: list with the same length as model, where each element identifies the items(rows) in the corresponding set of item parameters associated with the model(s) identified in model.

Details

The IRT models associated with the codes:

• drm:: dichotomous response models (includes 1PL, 2PL, and 3PL)
• gpcm:: generalized partial credit model (includes the partial credit model)
• grm:: graded response model
• mcm:: multiple-choice model
• nrm:: nominal response model

Author(s)

Jonathan P. Weeks weeksjp@gmail.com

Note

The names of the list elements for items must correspond to the elements in model. For example, if the poly.mod object is pm and the first element in pm@model is drm,one should be able to reference the associated items by pm@items$drm. If the list elements are unnamed, some functions may not work properly.

See Also

as.poly.mod, irt.pars, sep.pars, irt.prob