plot.pmatrix.class {mokken}

Plot pmatrix.class objects

Description

S3 Method to plot objects of class pmatrix.class. Graphic display of the checks of pmatrix. One graph for each item plotting the rows of the P(++) matrix and rows of the P(–) matrix. If nonintersection holds the lines in the plots of the P(++) matrix must be nondecreasing and the lines in the plots of the P(–) matrix nust be nonincreasing.

Usage

## S3 method for class 'pmatrix.class'
plot(x, items = all.items, pmatrix = "both", ci = TRUE, 
              alpha = .05, color = "black", transparancy = 20, ask = TRUE, ...)

Arguments

x

Object of class pmatrix.class produced by check.pmatrix.

items

vector containing the numbers of the item pairs for which the results are depicted graphically. Default the results for all items are depicted.

pmatrix

Valid options are "ppp", "pmm", and "both". If pmatrix="ppp", then the P(++) matrix is plotted, if pmatrix="pmm", then the P(–) matrix is plotted, if pmatrix="both", then both the P(++) matrix and P(–) matrix are plotted.

ci

Boolean. If TRUE, then confidence envelops are plotted around IRFs and ISRFs.

alpha

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

color

Color of the plotted curves and confidence envelops. Default is black.

transparancy

Transparancy of the confidence intervals. Higher values result in more opaque colors for the confidence intervals.

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

Details

The default graphic device in R may only display the last graph.

In the plot of the P(++) matrix and the P(–) matrix, the x-axis contains the k =(J-1)m item steps not pertaining to item j in order of popularity (ascending). Let Y_g=1 indicate that the g-th item step has been taken: i.e. Xi \geq y and let Y_g=0 indicate that the g-th item step has not been taken: i.e. Xi < y. The m lines in the plot of the P(++) matrix connect P(X_j \geq x, Y_1=1), \dots, P(X_j \geq x, Y_k=1)), x = 1, \dots m. The m lines in the plot of the P(–) matrix connect P(X_j < x, Y_1=0), \dots, P(X_j < x, Y_k=0)), x = 1, \dots, m.

If the number of item steps on the x-axis is greater than 10, then the labels are not displayed,

Value

Returns a graph.

Author(s)

L. A. van der Ark [e-mail]

References

Molenaar, I.W., & Sijtsma, K. (2000) User's Manual MSP5 for Windows [Software manual]. IEC ProGAMMA.

Sijtsma, K., & Molenaar, I. W. (2002) Introduction to nonparametric item response theory. Sage.

Van der Ark, L. A. (2007). Mokken scale analysis in R. Journal of Statistical Software. doi:10.18637/jss.v020.i11

See Also

check.pmatrix, summary.pmatrix.class

Examples

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