plot.rasch {ltm}R Documentation

Plot method for rasch objects

Description

Produces the Item Characteristic Curves for fitted rasch objects.

Usage

## S3 method for class 'rasch':
plot(x, items = NULL, legend = FALSE, cx = -3.4, cy = 0.9, ...)

Arguments

x an object inheriting from class rasch.
items a numeric vector denoting which items to plot; if NULL all items are plotted.
legend logical; if TRUE a legend is printed.
cx the x-coordinate to be passed to legend.
cy the y-coordinate to be passed to legend.
... extra graphical parameters to be passed to plot, lines and legend.

Details

Item characteristic curves (also known as item response functions) show how the probability of a positive response, in each item, increases with the values of the latent variable (ability).

Author(s)

Dimitris Rizopoulos dimitris.rizopoulos@med.kuleuven.be

See Also

rasch

Examples


## Item Characteristic Curves for the Wirs data;
## plot only items 1, 3 and 5:
m <- rasch(Wirs)
plot(m, items = c(1, 3, 5), lwd = 3, cex = 1.4)

## Item Characteristic Curves for the Lsat data;
## plot all items plus a legend
m <- rasch(Lsat)
plot(m, legend = TRUE, cx = 1.5, cy = 0.4, lwd = 3, cex = 1.4)


[Package ltm version 0.3-0 Index]