# Wright Map: IRT Item-Person Map This package allows the easy generation of `Wright Maps' (named after Ben Wright), also known as item-person maps to display unidimensional and multidimensional assessment results. These maps represent simultaneously the proficiency distribution of respondents and the item difficulty parameters as estimated by a model of the Rasch Family. The package contains several other functions for graphing common IRT statistics. Additionally, the package contains the `CQmodel` function, which reads output files created using ConQuest software and creates a set of data frames for easy data manipulation, bundled in a CQmodel object. The wrightMap function can take a CQmodel object as input or it can be used to create Wright Maps directly from data frames of person and item parameters. package ## Details ||| |:--|:--| |Package:|WrightMap| |Type:|Package| |Version:|1.0| |Date:|2014-03-02| |License:|BSD_3_clause \| LICENSE| The wrightMap function relies on two main inputs: (a) `thetas`: a vector or matrix of respondent proficiences, and (b) `thresholds`: a vector or matrix of item thresholds. In the simplest case, say for a unidimensional Rasch model, `thetas` can be a vector of person proficiencies and `thresholds` a vector of item difficulties. To plot multiple dimensions of person proficiency, simply provide them as a matrix were the results for each dimension is stored in a different column, such that for a 3-dimensional model with 1,000 persons, `theta` is a matrix of 1000 rows and 3 columns. To plot polytomous items, the thresholds for each level must be passed to the functions through the `thresholds` matrix, where each row represents an item and each column represents a level. For instance, if the results of a Rating Scale model with 5 response categories and 10 items is being plotted, the `thresholds` matrix will have 10 rows and 4 columns ( column one represents the thresholds between the 1 and 2 response category, column 2 the threshold between categories 2 and 3, etc.). Alternatively, wrightMap can read directly the `.shw` and `.eap/.mle/.wle` output files from a Conquest analysis, and will automatically generate the `thetas` and `thresholds` matrices. ## Author(s) David Torres Irribarra and Rebecca Freund Maintainer: David Torres Irribarra and Rebecca Freund ## References Andrich, D. (1978). A rating formulation for ordered response categories. **Psychometrika**, **43**(4), 561--573. Masters, G. N. (1982). A Rasch model for partial credit scoring. **Psychometrika**, **47**(2), 149--174. Wilson, M. (2005). Constructing measures: An item response modeling approach. Wright, B. D., & Stone, M. H. (1979). **Best test design.** Chicago: Mesa Press. ## Examples ```r # Plotting results of a unidimensional Rasch Model ## Mock results uni.proficiency <- rnorm(1000, mean = -0.5, sd = 1) difficulties <- sort( rnorm( 20)) ## Default map wrightMap( uni.proficiency, difficulties) ## Density version wrightMap( uni.proficiency, difficulties, person.side = personDens) # Plotting results of a multidimensional Rasch Model ## Mock results multi.proficiency <- data.frame( d1 = rnorm(1000, mean = -0.5, sd = 1), d2 = rnorm(1000, mean = 0.0, sd = 1), d3 = rnorm(1000, mean = +0.5, sd = 1)) difficulties <- sort( rnorm( 20)) dev.new(width=10, height=10) wrightMap( multi.proficiency, difficulties) # Plotting results of a unidimensional Rating Scale Model ## Mock results uni.proficiency <- rnorm(1000, mean = -0.5, sd = 1) items.loc <- sort( rnorm( 20)) thresholds <- data.frame( l1 = items.loc - 0.5, l2 = items.loc - 0.25, l3 = items.loc + 0.25, l4 = items.loc + 0.5) dev.new(width=10, height=10) wrightMap( uni.proficiency, thresholds) ## Setting up labels, colors and symbols thresholds.labels <- data.frame( l1 = paste('Lev',rep(1,20),sep = ''), l2 = paste('Lev',rep(2,20),sep = ''), l3 = paste('Lev',rep(3,20),sep = ''), l4 = paste('Lev',rep(4,20),sep = '')) thresholds.colors <- data.frame( l1 = rep( 'green',20), l2 = rep( 'red',20), l3 = rep( 'yellow',20), l4 = rep( 'blue',20)) thresholds.symbols <- data.frame( l1 = rep( 15,20), l2 = rep( 16,20), l3 = rep( 17,20), l4 = rep( 18,20)) dev.new(width=10, height=10) wrightMap( uni.proficiency, thresholds , thr.lab.text = thresholds.labels , thr.lab.col = as.vector(as.matrix(thresholds.colors)) , thr.sym.pch = thresholds.symbols ) ```

WrightMap-package