unimirt.plot: IRT plots

In CambridgeAssessmentResearch/unimirt: Applications of Unidimensional IRT using the R Package 'mirt'

IRT plots

Description

For unidimensional IRT models this function produces the standard types of plot associated with IRT including: item and test information functions, item and test characteristic curves and item category probability trace plots. In contrast to the function "itemplot" in the mirt package this function is based around ggplots which makes it easier for users to reformat and customise the look of these plots.

Usage

unimirt.plot(
  mirtobj,
  type,
  which.items = NULL,
  thetamin = NULL,
  thetamax = NULL
)

Arguments

mirtobj	An estimated IRT model (of class SingleGroupClass) estimated either using mirt or unimirt.
type	The type of plot to produce. "trace" produces category probability tracce plots, "cumtrace" produces cumulative probability curve (the chance of achieving each category or above), "infotrace" produces item information curves for each item, "itemscore" produces item characteristic curves for each item, "info" produces total test information (based on selected items), "SE" produces an idea of the precision of ability estimates based on the selected items, and "score" gives the test characteristic curve (based on the selected items).
which.items	an integer vector indicating which items to include. By default all items are included.
thetamin	The minimum ability to include in plots. By default this is extracted from the mirtobj object.
thetamax	The maximum ability to include in plots. By default this is extracted from the mirtobj object.

Value

A ggplot.

Examples

## Not run: 
mirt1=unimirt(mathsdata)
unimirt.plot(mirt1,"trace",which.items=34,thetamin=-4,thetamax=4)
unimirt.plot(mirt1,"trace",which.items=c(1,9),thetamin=-4,thetamax=4)
unimirt.plot(mirt1,"trace",which.items=c(1,9,12,34),thetamin=-4,thetamax=4)
unimirt.plot(mirt1,"cumtrace",which.items=34,thetamin=-4,thetamax=4)
unimirt.plot(mirt1,"infotrace",which.items=c(1,9,12,34),thetamin=-4,thetamax=4)
unimirt.plot(mirt1,"itemscore",which.items=c(1,9,12,34),thetamin=-4,thetamax=4)
unimirt.plot(mirt1,"info",which.items=c(1,9,12,34),thetamin=-4,thetamax=4)
unimirt.plot(mirt1,"SE",which.items=c(1,9,12,34),thetamin=-4,thetamax=4)
unimirt.plot(mirt1,"score",which.items=c(1,9,12,34),thetamin=-2,thetamax=3)

## End(Not run)

CambridgeAssessmentResearch/unimirt documentation built on June 10, 2025, 6:03 a.m.