eRm: plotPWmap – R documentation

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plotPWmap

Pathway Map

Description

A Bond-and-Fox Pathway Map displays the location of each item or each person against its infit t-statistic. Pathway maps are useful for identifying misfitting items or misfitting persons. Items or people should ideally have a infit t-statistic lying between about -2 and +2, and these values are marked.

Usage

plotPWmap(object, pmap = FALSE, imap=TRUE,
                 item.subset = "all", person.subset = "all",
                 mainitem = "Item Map", mainperson = "Person Map",
                 mainboth="Item/Person Map",
                 latdim = "Latent Dimension",
                 tlab = "Infit t statistic",
                 pp = NULL, cex.gen = 0.6, cex.pch=1,
                 person.pch = 1, item.pch = 16,
                 personCI = NULL, itemCI = NULL, horiz=FALSE)

Arguments

`object`	Object of class `Rm` or `dRm`
`pmap`	Plot a person map if `TRUE`; the default is `FALSE`.
`imap`	Plot an item map if `TRUE` (the default); do not plot if `FALSE`. At least one of `pmap` and `imap` must be `TRUE`.
`item.subset`	Subset of items to be plotted for an item map. Either a numeric vector indicating the item numbers or a character vector indicating the item names. If `"all"`, all items are plotted. The number of items to be plotted must be > 1.
`person.subset`	Subset of persons to be plotted for a person map. Either a numeric vector indicating the person numbers or a character vector indicating the person names. If `"all"`, all persons are plotted. The number of persons to be plotted must be > 1.
`mainitem`	Main title of an item plot.
`mainperson`	Main title of a person plot.
`mainboth`	Main title of a person/item joint plot.
`latdim`	Label of the y-axis, i.e., the latent dimension.
`tlab`	Label of the x-axis, i.e., the t-statistic dimension.
`pp`	If non-`NULL`, this contains the `person.parameter` data of the data object, avoiding the need to recalculate it.
`cex.gen`	`cex` as a graphical parameter specifies a numerical value giving the amount by which plotting text and symbols should be magnified relative to the default. Here `cex.gen` applies to all text labels. The default is 0.6.
`cex.pch`	applies to all plotting symbols. The default is 1.
`person.pch, item.pch`	Specifies the symbol used for plotting person data and item data respectively; the defaults are 1 and 16 respectively. See `points` for more information about `pch` values.
`personCI, itemCI`	Plotting confidence intervals for the the person abilities and item difficulties. If `personCI=NULL` (the default) no confidence intervals are drawn for person abilities. Otherwise, specifying `personCI` draws approximate confidence intervals for each person's ability. `personCI` must be specified as a list, and the optional elements of this list are `gamma`, the confidence level, `col`, colour, and `lty`, line type. If `personCI` is specified as an empty list, or not all of the list items are specified, the default values `personCI=list(gamma=0.95,col="orange",lty="dotted")` will be used. The same goes for `itemCI`, except that the default settings are `itemCI=list(gamma=0.95,col="red",lty="dotted")`.
`horiz`	if `TRUE`, the plot is horizontal, i.e., the latent dimension is on the x-axis. The default is `FALSE`.

Details

This code uses vertical(horizontal) error bars rather than circles or boxes to indicate standard errors. It also offers the possibility of plotting item or person data on its own; this can considerably simplify the reading of the plots for large datasets.

Author(s)

Julian Gilbey

References

Bond T.G., Fox C.M. (2007) Applying the Rasch Model: Fundamental Measurement in the Human Sciences (2nd ed.) chapter 3, Lawrence Erlbaum Associates, Inc.

Linacre J.M., Wright B.D. (1994) Dichotomous Infit and Outfit Mean-Square Fit Statistics / Chi-Square Fit Statistics. Rasch Measurement Transactions 8:2 p. 350, https://www.rasch.org/rmt/rmt82a.htm

Linacre J.M. (2002) What do Infit and Outfit, Mean-square and Standardized mean? Rasch Measurement Transactions 16:2 p. 878, https://www.rasch.org/rmt/rmt162f.htm

Wright B.D., Masters G.N. (1990) Computation of OUTFIT and INFIT Statistics. Rasch Measurement Transactions 3:4 p. 84–85, https://www.rasch.org/rmt/rmt34e.htm

Examples

res <- PCM(pcmdat)
pparm <- person.parameter(res)
plotPWmap(res, pp = pparm)
plotPWmap(res, pp = pparm, pmap = TRUE)

eRm

Extended Rasch Modeling

v1.0-2

GPL-3

Authors

Patrick Mair [cre, aut], Reinhold Hatzinger [aut], Marco J. Maier [aut], Thomas Rusch [ctb], Rudolf Debelak [ctb]

Initial release

2021-02-11