ggWrightMap: Wright Map using ggplot

In kitdouble/ShinyIRT: Test and Item Analysis via Shiny

Description

This function allows to generate Wright Map (also called item-person map) using ggplot() function from package ggplot2. Wright Map is used to display histogram of factor scores and the item difficulty parameters estimated by the Rasch IRT model.

Usage

ggWrightMap(theta, b, binwidth = 0.5, color = "blue", size = 15)

Arguments

theta	numeric: vector of ability estimates
b	numeric: vector of difficulty estimates
binwidth	numeric: the width of the bins of histogram
color	character: color of histogram
size	text size in pts

Author(s)

Adela Drabinova
Institute of Computer Science, The Czech Academy of Sciences
Faculty of Mathematics and Physics, Charles University
[e-mail]

Patricia Martinkova
Institute of Computer Science, The Czech Academy of Sciences
[e-mail]

References

Wright, B. D., & Stone, M. H. (1979). Best test design.

See Also

wrightMap

Examples

## Not run: 
library(ShinyItemAnalysis)
library(mirt)

data(dataMedical)
data <- dataMedical[, 1:100]

# Model
fit <- mirt(data, model = 1, itemtype = "Rasch")
# factor scores
theta <- as.vector(fscores(fit))
# difficulty estimates
b <- coef(fit, simplify = T)$items[, "d"]

ggWrightMap(theta, b)

## End(Not run)

kitdouble/ShinyIRT documentation built on May 3, 2019, 5:47 p.m.