Save a plot for every item — save_item

Writes one plot per item – the item characteristic curve, category probability curves, threshold probability curves, or category frequencies – to a single multi-page PDF or a ZIP archive of PNGs, chosen by the extension of file.

Usage

save_item_plots(
  fit,
  what = c("icc", "ccc", "tpc", "cfreq"),
  file,
  items = NULL,
  n_groups = fit$n_groups,
  grid = seq(-5, 5, 0.05),
  observed = TRUE,
  width = 8,
  height = 5.5,
  dpi = 300
)

Arguments

fit: A fitted object from rasch.
what: Which plot: "icc", "ccc", "tpc", or "cfreq".
file: Output path ending in .pdf (one page per item) or .zip (one PNG per item).
items: Item names or indices; all items by default.
n_groups: Class intervals for observed overlays.
grid: Logit grid for the curves.
observed: Overlay observed proportions on the category and threshold probability curves.
width, height, dpi: Device size in inches and PNG resolution.

Value

Invisibly, the output path.

Examples

set.seed(1)
d <- seq(-2, 2, length.out = 6)
X <- matrix(rbinom(400 * 6, 1, plogis(outer(rnorm(400), d, "-"))), 400, 6)
colnames(X) <- paste0("I", 1:6)
f <- rasch(X)
save_item_plots(f, "icc", file.path(tempdir(), "icc_all.pdf"))