Item characteristic (trace) curves

Item characteristic (trace) curves

Usage

gg_trace(
  x,
  which.items = NULL,
  type = c("prob", "expected"),
  facet = TRUE,
  theta_lim = c(-4, 4)
)

Arguments

x

a unidimensional model returned by mirt::mirt().

which.items

items to plot, by position or name. Defaults to all.

type

"prob" for category probability curves or "expected" for the expected item score.

facet

logical; one panel per item. If FALSE all items share one panel (only sensible for type = "expected" or dichotomous items).

theta_lim

range of the latent trait.

Value

A ggplot object.

Examples

mod <- mirt(expand.table(LSAT7), 1, verbose = FALSE)
gg_trace(mod)

gg_trace(mod, facet = FALSE)