ggIRT

Overview

The ggIRT R package provides functions for visualizing the results of analyses using the mirt or ltm packages. The following can be done with this package:

• Visualization of item characteristic curves (gg_irccc)
  
• Visualization of item response category characteristic curves (gg_irccc)
  
• Visualization of test information curves (gg_tic)
  
• Visualization of item information curves (gg_iic)

The following functions are not implemented, but these are planned to be added in the future

• Visualization of ICC for multiple group
  
• Visualization of IRCCC for multiple group
  
• Visualization of test characteristic curves

Installation

You can install the development version of ggIRT from GitHub with:

# install.packages("devtools")
devtools::install_github("hedgehog2nd/ggIRT")

Usage

After installation, you can load this package by using the library function. You can draw an IRCCC by passing the analysis results res and item numbers of the mirt package as arguments to the gg_irccc function. If you set the grm argument to FALSE, you can draw the ICC for a binary IRT. The ggplot2 is used for visualization. It is also possible to change axis labels and apply original themes.
You can draw a TIC by passing the analysis results of the mirt package as an argument to the gg_tic function.

library(ggIRT)
library(mirt)

res <- mirt(data, itemtype = "graded")

gg_irccc(res, item = 1)
gg <- gg_irccc(res, item = 1)
gg + theme_bw() + labs(x = "THETA", y = "PROB.", title = "IRCCC item 1")

gg_tic(res)

Functions

• gg_irccc: Visualize Item Response Category Characteristic Curves (IRCCC) from mirt or ltm object.detail
• gg_iic: Visualize Item Information Curves (IIC) from mirt or ltm object.detail
• gg_tic: Visualize Test Information Curves (TIC) from mirt or ltm object.detail

Depends

This package requires the following:

• R (>= 4.1.0)
  
• ggplot2
  
• mirt
  
• ltm

Version History

version 1.0.0
Updated on March 26, 2025 (JST)

• Create a README file.
  
• Create a help file.
  
• Item information curve output is now supported (gg_iic).
  
• gg_tic function now supports ltm and grm objects.
• gg_tic function now supports binary IRT.
• To avoid a conflict with the ltm function, the ltm argument has been changed to use_ltm.
  
• fix gg_irccc function.

version 0.1.0
March 24, 2025 (JST)

• released