A matrix of responses to multiple-choice items: persons as
rows, items as columns. As a rare exception in <code>irtoys</code>, responses must
not be recoded to 0/1, and there may be missing responses.

choices

A vector containing the key (correct answers) to the items in
<code>choices</code>.

A single number pointing to the item (column of <code>choices</code>)
to plot.

item

The main title of the plot, given that <code>add=F</code>.

main

The colour of the curves. Default is 1 for black. Use <code>co=NA</code>
to plot each curve in a different colour.

When <code>label=T</code>, individual curves will be labeled with the
item number.

label

A plotting function producing non-parametric analogues of the IRF for each
option in a multiple choice item not unlike those in Jim Ramsay's TestGraf
program.

models

A collection of functions useful in learning and practicing IRT,
which can be combined into larger programs. Provides basic CTT analysis,
a simple common interface to the estimation of item
parameters in IRT models for binary responses with three different programs
(ICL, BILOG-MG, and ltm), ability estimation (MLE, BME, EAP, WLE, plausible
values), item and person fit statistics, scaling methods (MM, MS, Stocking-Lord,
and the complete Hebaera method), and a rich array of parametric and
non-parametric (kernel) plots. Estimates and plots Haberman's interaction model
when all items are dichotomously scored.

tgf: Non-parametric option curves

Description

Usage

Arguments

References

See Also

Examples