Wright Map item sides
Draw the item side of a Wright Map in a variety of styles. Intended to be primarily called by wrightMap, but also available for use on their own.
itemModern(thr, yRange = NULL, axis.items = "Items", show.thr.sym = TRUE , thr.sym.cex = 0.8, thr.sym.lwd = 1, thr.sym.pch = 23 , thr.sym.col.fg = rgb(0, 0, 0, 0.3), thr.sym.col.bg = rgb(0, 0, 0, 0.3) , show.thr.lab = TRUE, thr.lab.pos = c(2, 4), thr.lab.text = NULL , thr.lab.col = "black", thr.lab.cex = 0.5, thr.lab.font = 2, label.items.rows = 1 , label.items.srt = 0, label.items = NULL, label.items.cex = 0.6 , label.items.ticks = TRUE, axis.logits = "Logits", show.axis.logits = "R" , oma = c(0, 0, 0, 3), cutpoints = NULL, vertLines = FALSE, ...) itemClassic(thr, yRange = NULL, axis.items = "Items", axis.logits = "Logits" , show.axis.logits = "R", oma = c(0, 0, 0, 3), cutpoints = NULL, ...) itemHist(thr, yRange = NULL, axis.items = "Items", axis.logits = "Logits" , show.axis.logits = "R", oma = c(0, 0, 0, 3), cutpoints = NULL,...)
General arguments:
thr |
vector or matrix of threshold parameters. If a matrix, items should be in the rows and steps in the columns. |
yRange |
vector with 2 elements specifying the lower and upper limits of the plot's y-axis. |
axis.items |
title of the x-axis. |
axis.logits |
title of the y-axis. |
show.axis.logits |
if equal to "R" or "L", draws a logit axis on the right or left. Will also draw an axis on the right if the value is codeTRUE. If any other value, the axis is not drawn. |
oma |
values to use for the |
cutpoints |
values at which to draw horizontal lines (see |
... |
additional arguments to |
itemModern arguments:
show.thr.sym |
logical. If |
thr.sym.cex |
an integer, vector or matrix of numerical values giving the amount by which the threshold symbols should be magnified relative to the default. |
thr.sym.lwd |
an integer, vector or matrix of positive numbers specifying the width of the lines used in the threshold symbols. |
thr.sym.pch |
an integer, vector or matrix of integers specifying a symbol or a single character to be used to represent the item thresholds. |
thr.sym.col.fg |
an integer, vector or matrix of numerical values indicating the foreground color to be used in the thresholds labels. |
thr.sym.col.bg |
an integer, vector or matrix of numerical values indicating the background color to be used in the thresholds labels. |
show.thr.lab |
logical. If |
thr.lab.pos |
an integer, vector or matrix containing the position in which to display the label for each threshold label. Values of 1, 2, 3 and 4, respectively indicate positions below, to the left of, above and to the right of the specified coordinates. |
thr.lab.text |
a matrix containing the labels to display for each threshold. In the matrix each row represents an item and each column represents a level. |
thr.lab.col |
a matrix containing the color to display for each threshold label. In the matrix each row represents an item and each column represents a level. |
thr.lab.cex |
an integer, vector or matrix of numerical values giving the amount by which the threshold labels should be magnified relative to the default. |
thr.lab.font |
an integer, vector or matrix which specifies which font to use for threshold labels. 1 corresponds to plain text , 2 to bold face (the default), 3 to italic and 4 to bold italic. |
label.items.rows |
an integer indicating the number of rows used to display the item labels. Can take values 1 (default), 2 and 3. Useful when item labels are overlaping. |
label.items.srt |
angle of rotation for item labels. It only works if |
label.items |
a vector of strings containing the labels identifying the items. |
label.items.cex |
an integer, vector or matrix of numerical values giving the amount by which the threshold labels should be magnified relative to the default. |
label.items.ticks |
logical. If |
vertLines |
logical. If |
These functions are designed as helper functions for wrightMap to draw the item side of a map. When called outside of that function, they can be used to create more customized maps. Possible uses inlcude:
draw an item map on its own
compare two item maps in a single figure
draw a Wright Map with the item side on the left and the person side on the right
etc.
The itemClassic style draws a stacked plot, similar to the Wright Maps available in ConQuest text output files. The itemModern style is the default style for wrightMap which plots each item as a column of difficulty parameters. The itemHist style plots a histogram.
When combining with a person.side function, note that those functions use split.screen, which are incompatible with layout and some other plotting functions. Note also that all graphs on a single plot should usually have their yRange explicitly specified to ensure that values are comparable across plots. To plot data from ConQuest output, use itemData first to extract the data table.
Rebecca Freund and David Torres Irribarra
#As a call from wrightMap:
## 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)
## 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))
wrightMap( uni.proficiency, thresholds
, thr.lab.text = thresholds.labels
, thr.lab.col = thresholds.colors
, thr.sym.pch = thresholds.symbols
)
#As direct call:
## Plotting results of a unidimensional Rating Scale Model
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)
itemModern(thresholds)
itemClassic(thresholds)
itemHist(thresholds)
## Plotting ConQuest results
fpath <- system.file("extdata", package="WrightMap")
model1 <- CQmodel(file.path(fpath,"ex2a.eap"), file.path(fpath,"ex2a.shw"))
m1.item <- itemData(model1)
#control of oma allows us to give more space to longer item names
itemModern(m1.item, label.items.srt= 90, oma = c(3,0,0,3))
itemClassic(m1.item)
itemHist(m1.item)
## Creating a Wright Map with item side on the left
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))
# split.screen: Set up a split screen with the left side 80 percent of the screen
# yRange = c(-3,4): Set the yRange to be the same for both sides
# axis.logits.side = "L": Move the item logit axis to the left
# oma = c(0,0,0,2): Adjust the spacing between the graphs
# mtext("Wright Map", side = 3, font = 2, line = 1): add a title
# screen(2): Start drawing on the second screen
split.screen(figs = matrix(c(0,.8,0,1,.8,1,0,1),ncol = 4, byrow = TRUE))
itemModern(thresholds, yRange = c(-3,4), show.axis.logits = "L", oma = c(0,0,0,2))
mtext("Wright Map", side = 3, font = 2, line = 1)
screen(2)
personHist(multi.proficiency, axis.persons = "",yRange = c(-3,4)
, axis.logits = "Persons", show.axis.logits = FALSE)
## Creating a multidimensional Wright Map with each dimension separate
## Mock results
d1 = rnorm(1000, mean = -0.5, sd = 1)
d2 = rnorm(1000, mean = 0.0, sd = 1)
dim1.diff <- rnorm(5)
dim2.diff <- rnorm(5)
dev.new(width=10, height=10)
split.screen(figs = matrix(c(0,.1,0,1,
.12,.6,0,1,
.5,.6,0,1,
.5,1,0,1),ncol = 4,byrow = TRUE))
personDens(d1,yRange = c(-3,3),show.axis.logits = FALSE,axis.logits = "")
screen(2)
itemModern(dim1.diff,yRange = c(-3,3),show.axis.logits = FALSE)
mtext("Wright Map", side = 3, font = 2, line = 1)
screen(3)
personDens(d2,yRange = c(-3,3),show.axis.logits = FALSE,axis.logits = ""
,axis.persons = "",dim.names = "Dim2")
screen(4)
itemModern(dim2.diff,yRange = c(-3,3),show.axis.logits = FALSE
,label.items = paste("Item",6:10))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.