mokken (version 2.7.3)

plot.iio.class: Plot iio.class objects

Description

S3 Method to plot objects of class iio.class. Graphic display of the checks of iio. One graph for each item plotting the estimated item response functions.

Usage

## S3 method for class 'iio.class':
plot(x, item.pairs = all.pairs, plot.ci = TRUE, color.ci = c("orange","yellow"), alpha.ci = .05, ask = TRUE, ...)

Arguments

x

Object of class iio.class produced by check.iio.

item.pairs

vector containing the numbers of the item pairs for which the results are depicted graphically. For example, item.pairs = 1 prints the results for items 1 and 2, item.pairs = 2 prints the results for items 1 and 3,

plot.ci

Boolean. If TRUE (default), then confidence envelops are plotted around ISRFs.

color.ci

Color of the plotted confidence envelops. Defaults are orange for the first item and yellow for the second item.

alpha.ci

Type of plotted (1 - alpha) confidence intervals. By default 95-percent confidence intervals are depicted

ask

Boolean. If TRUE (default), then par("ask"=TRUE); i.e., a hard return between subsequent plots is required. If FALSE, then par("ask"=FALSE).

...

Optional graphical parameters will be ignored

Value

• Returns a graph.

Details

The plot function corresponds to method MIIO; each graph plots the estimated item response functions (item rest-score functions) for two items. For details of the method, see Ligtvoet et al. (2010, 2011); Sijtsma et al. (2012). For details of the confidence envelopes, see Van der Ark (2012b). For the implementation in R, see Van der Ark (2012a). For ask==FALSE, the default graphic device in R may only display the last graph.

References

Ligtvoet, R., L. A. van der Ark, J. M. te Marvelde, and K. Sijtsma (2010). Investigating an invariant item ordering for polytomously scored items. Educational and Psychological Measurement, 70, 578-595. Ligtvoet, R., L. A. van der Ark, W. P. Bergsma, and K. Sijtsma (2011). Polytomous latent scales for the investigation of the ordering of items. Psychometrika, 76, 200-216. Sijtsma, K., R. R. Meijer, and L. A. van der Ark (2011). Mokken scale analysis as time goes by: An update for scaling practitioners. Personality and Individual Differences, 50, 31-37. Van der Ark, L. A. (2012a). New developments in Mokken scale analysis in R. Journal of Statistical Software, 48 (5), 1-27. http://www.jstatsoft.org/v20/i11 Van der Ark, L. A. (2012b). Visualization of nonparametric IRT models. Paper presented at the Annual Meeting of the Psychometric Society, Lincoln NE, July, 2012.

See Also

check.iio, summary.iio.class

Examples

data(acl)
Communality <- acl[,1:10]
iio.list <- check.iio(Communality)
summary(iio.list)
plot(iio.list)