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Item response theory motif (crossed persons x items)

Source: R/motifs.R
umg_irt.Rd

Builds a unidimensional IRT diagram with crossed person and item plates: a latent ability in the person plate, item parameters as fixed unknowns in the item plate, and an observed categorical response at the crossing.

Usage

umg_irt(
  model = c("2PL", "1PL", "3PL", "graded", "PCM", "GPCM"),
  ability = "theta",
  n_dim = 1L
)

Arguments

model

Item model. Dichotomous: "1PL", "2PL", "3PL". Polytomous: "graded" (graded response model, GRM), "PCM" (partial credit model), "GPCM" (generalized partial credit model). The choice controls which item-parameter diamonds are drawn (discrimination, difficulty/thresholds, guessing).

ability

Name/label stem for the latent ability.

n_dim

Number of latent ability dimensions (>= 1). With more than one dimension the model is multidimensional IRT (MIRT); each ability vertex points at the response.

Value

An object of class umg.

Examples

plot(umg_irt("2PL"))

plot(umg_irt("graded"))

plot(umg_irt("2PL", n_dim = 2))