irt.pars-class {plink}

Class "irt.pars"

Description

The formal S4 class for irt.pars. This class contains the item parameters and characteristics of the item parameters for one or more groups. When parameters are included for two or more groups, the common items between the different groups are also included.

Details

Objects of class irt.pars contain all the information necessary to produce expected response probabilities, linking constants (when data for two or more groups are included), and to plot item response curves/surfaces, vector plots, and parameter comparison plots.

Objects from the Class

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

Slots

pars:

matrix of item parameters for a single group or a list of matrices containing item parameters for two or more groups

cat:

vector with length equal to the number of items, identifying the number of response categories for each item for a single group or a list of response category vectors for two or more groups

poly.mod:

a poly.mod object for one group or a list of poly.mod objects identifying the items associated with each IRT model (see class poly.mod for more information)

common:

a j x 2 matrix for j common items or a list of matrices identifying the common items between pairs of item parameters

location:

logical vector identifying whether a given set of item parameters (i.e., for a given group) includes a location parameter

groups:

the number of groups (i.e. sets of item parameters)

dimensions:

numeric vector identifying the number of modeled dimensions

Extends

Class poly.mod, directly. Class list.poly, by class poly.mod, distance 2.

Author(s)

Jonathan P. Weeks [e-mail]

See Also

as.irt.pars, as.poly.mod