irt.pars-class function

Class "irt.pars"

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. class

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

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.

Extends

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

Author(s)

Jonathan P. Weeks weeksjp@gmail.com

See Also

as.irt.pars, as.poly.mod