Plot Test Information Curve (TIC) from exametrika

This function takes exametrika IRT or GRM output as input and generates a Test Information Curve (TIC) using ggplot2. TIC shows the total information provided by all items at each ability level.

Usage

plotTIC_gg(
  data,
  xvariable = c(-4, 4),
  title = TRUE,
  colors = NULL,
  linetype = "solid",
  show_legend = FALSE,
  legend_position = "right"
)

Arguments

data: An object of class c("exametrika", "IRT") from exametrika::IRT() or c("exametrika", "GRM") from exametrika::GRM().
xvariable: A numeric vector of length 2 specifying the range of the x-axis (ability). Default is c(-4, 4).
title: Logical or character. If TRUE (default), display an auto-generated title. If FALSE, no title. If a character string, use it as a custom title.
colors: Character vector. Color(s) for the curve. If NULL (default), a colorblind-friendly palette is used.
linetype: Character or numeric specifying the line type. Default is "solid".
show_legend: Logical. If TRUE, display the legend. Default is FALSE.
legend_position: Character. Position of the legend. One of "right" (default), "top", "bottom", "left", "none".

Value

A single ggplot object showing the Test Information Curve.

Details

The Test Information Function is the sum of all Item Information Functions. It indicates how precisely the test as a whole measures ability at each point on the theta scale. The reciprocal of test information is approximately equal to the squared standard error of measurement.

The function supports IRT models (2PL, 3PL, 4PL) and GRM.

Examples

library(exametrika)
# \donttest{
# IRT example
result_irt <- IRT(J15S500, model = 3)
plot_irt <- plotTIC_gg(result_irt)
plot_irt # Show Test Information Curve


# GRM example
result_grm <- GRM(J5S1000)
plot_grm <- plotTIC_gg(result_grm)
plot_grm # Show Test Information Curve

# }