raschmix-plot-method {psychomix}

Profile Plot of Item Parameters

Description

The plot method for raschmix-class objects gives a base plot of the item parameter profiles in each class. A lattice plot of the item parameters is returned by xyplot. A rootogram or histogram of the posterior probabilities is plotted via histogram.

Usage

## S4 method for signature 'raschmix,missing'
plot(x, y, component = NULL, difficulty = TRUE,
                   center = TRUE, index = TRUE, names = TRUE,
                   abbreviate = FALSE, ref = TRUE, col =  "black",
                   refcol = "lightgray", linecol = NULL, lty = 2, cex = 1,
                   pch = 19, type = NULL, ylim = NULL, xlab = "Items",
                   ylab = NULL, legend = TRUE, pos = "topright",
                   srt = 45, adj = c(1.1, 1.1), ...)
## S3 method for class 'raschmix'
histogram(x, data, root = TRUE, ...)
## S3 method for class 'raschmix'
xyplot(x, data, component = NULL, item = NULL,
  difficulty = TRUE, plot.type = c("multiple", "single"),
  auto.key = NULL, type = "b", lty = NULL, xlab = "Item", ylab = NULL,
  panel = NULL, scales = NULL, ...)

Arguments

x

An object of class "raschmix".

y

Not used.

component

A vector indicating which components should be plotted.

difficulty

Logical. Should item difficulty parameters be used?

center

Logical. Should the item parameters be centered around 0?

index

Logical. Should the index be used for labelling the items?

names

Either logical or an optional vector of names used for labeling of the items.

abbreviate

Logical. Should the labels of the items be abbreviated?

ref

Logical. Should a reference line be drawn?

col

Point color. If col is a vector, it is interpreted as the color of the components respectively. Individual coloring within components is possible if col is given as a matrix with each column representing one component.

refcol

Color of the reference line.

linecol

Line color. Defaults to the point color.

lty, cex, pch, type, ylim, xlab, ylab

Further standard graphical parameters.

legend

Logical. Should a legend be included?

pos

Position of the legend.

srt, adj

Passed on to text() if names = TRUE.

...

Further graphical parameters.

data

Ignored.

root

Logical. Should a rootogram be drawn?

item

A vector indicating which items should be plotted.

plot.type

Should the item profiles be drawn in multiple panels or a single panel?

auto.key, panel, scales

Further graphical parameters for lattice.

Details

For a graphical representation of the item parameter in each class use plot (for a base graph) or xyplot (for a lattice plot).

For a graphical representation of the quality of the mixture use histogram. For details see plot-methods.

References

Frick, H., Strobl, C., Leisch, F., and Zeileis, A. (2012). Flexible Rasch Mixture Models with Package psychomix. Journal of Statistical Software, 48(7), 1–25. http://www.jstatsoft.org/v48/i07/.

Leisch, F. (2004). FlexMix: A General Framework for Finite Mixture Models and Latent Class Regression in R. Journal of Statistical Software, 11(8), 1–18. http://www.jstatsoft.org/v11/i08/.

Leisch, F. (2004). Exploring the Structure of Mixture Model Components. In Jaromir Antoch, editor, Compstat 2004 – Proceedings in Computational Statistics, pages 1405–1412. Physika Verlag, Heidelberg, Germany. ISBN 3-7908-1554-3.