irtoys: plot.irf – R documentation

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plot.irf

A plot method for item response functions

Description

Useful for plotting item response functions. The x argument of irf should better be left out unless something special is required.

Usage

## S3 method for class 'irf'
plot(x, add = FALSE, main = "Item response function",
  co = 1, label = FALSE, ...)

Arguments

`x`	An object produced by function `irf`
`add`	When `add=T`, the IRF is added to a plot, otherwise a new plot is started. Default is F.
`main`	The main title of the plot, given that `add=F`.
`co`	The colour of the IRF curve. Default is 1 for black. Use `co=NA` to plot each IRF in a different colour.
`label`	When `label=T`, individual curves will be labeled with the item number.
`...`	Any additional plotting parameters

Author(s)

Ivailo Partchev

Examples

# plot IRF for all items in red, label with item number
plot(irf(Scored2pl), co="red", label=TRUE)
# plot IRF for items 2, 3, and 7 in different colours
plot(irf(Scored2pl, items=c(2,3,7)), co=NA)

irtoys

A Collection of Functions Related to Item Response Theory (IRT)

v0.2.1

GPL (>= 2)

Authors

Ivailo Partchev [aut, cre], Gunter Maris [aut], Tamaki Hattori [ctb]

Initial release

2017-12-15