This package uses item response theory methods to compute
linking constants and conduct chain linking of unidimensional
or multidimensional tests for multiple groups under a common
item design.  The unidimensional methods include the Mean/Mean,
Mean/Sigma, Haebara, and Stocking-Lord methods for dichotomous
(1PL, 2PL and 3PL) and/or polytomous (graded response, partial
credit/generalized partial credit, nominal, and multiple-choice
model) items.  The multidimensional methods include the least
squares method and extensions of the Haebara and Stocking-Lord
method using a single dilation parameter, multiple dilation
parameters, or the Oshima, Davey, & Lee approach for
multidimensional extensions of all the unidimensional
dichotomous and polytomous item response models.  The package
also includes functions for importing item and/or ability
parameters from common IRT software, conducting IRT true score
and observed score equating, and plotting item response
curves/surfaces, vector plots, and comparison plots for
examining parameter drift.

This package uses item response theory methods to compute
linking constants and conduct chain linking of unidimensional
or multidimensional tests for multiple groups under a common
item design.  The unidimensional methods include the Mean/Mean,
Mean/Sigma, Haebara, and Stocking-Lord methods for dichotomous
(1PL, 2PL and 3PL) and/or polytomous (graded response, partial
credit/generalized partial credit, nominal, and multiple-choice
model) items.  The multidimensional methods include the least
squares method and extensions of the Haebara and Stocking-Lord
method using single or multiple dilation parameters for
multidimensional extensions of all the unidimensional
dichotomous and polytomous item response models.  The package
also includes functions for importing item and/or ability
parameters from common IRT software, conducting IRT true score
and observed score equating, and plotting item response
curves/surfaces, vector plots, and comparison plots for
examining parameter drift.