pair_gen_anchors: pair_gen_anchors

In IRTM: Theory-Driven Item Response Theory (IRT) Models

pair_gen_anchors

Description

This function generates anchor points from the M matrices. It creates d(d-1)*4 fake respondents such that, for every pair of dimensions: The first respondent has an extremely positive value of both dimensions of the pair, The second has an extremely positive value for dim 1 and an extremely negative value for dim 2 of each pair, The third has an extremely negative value for dim 1 and an extremely positive value for dim 2 of each pair, The fourth has an extremely negative value of both dimensions of the pair. These respondents' answers are imputed according to the directions of loadings specified by the M-matrices, i.e., if question k loads positively on dim 1 and positively on dim 2, the first respondent in the dim 1/dim 2 pair will have yes for question k. If question k+1 loads positively on dim 1 and negatively on dim 2 then the second respondent in the dim 1/dim 2 pair will have yes on question k+1 and so on.

Usage

pair_gen_anchors(M, A)

Arguments

M	a list containing K dxd M-matrices
A	What value should be considered extreme for the latent dimensions.

Value

A list with two elements:

Yfake	A matrix of dimension (d(d-1)*4 x K) containing the imputed answers of the fake anchor respondents, where d is the number of dimensions and K is the number of questions. Values are 0 (no) or 1 (yes).
theta_fake	A list of d(d-1)*4 vectors, each of length d, representing the latent trait values for the fake anchor respondents. Each vector contains mostly zeros, with extreme values (A or -A) at the positions corresponding to the pair of dimensions being considered.

IRTM documentation built on June 8, 2025, 10:46 a.m.