tgf function

Non-parametric option curves

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.

tgf(
  choices,
  key,
  item,
  main = "Non-parametric response function",
  co = 1,
  label = FALSE
)

Arguments

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

• key: A vector containing the key (correct answers) to the items in choices.

• item: A single number pointing to the item (column of choices) to plot.

• main: The main title of the plot, given that add=F.

• co: The colour of the curves. Default is 1 for black. Use co=NA

  to plot each curve in a different colour.

• label: When label=T, individual curves will be labeled with the item number.

Examples

key=c(2,3,1,1,4,1,2,1,2,3,3,4,3,4,2,2,4,3)
tgf(choices=Unscored, key=key, item=4, co=NA, label=TRUE)

References

James O. Ramsay (2000). TestGraf: A program for the graphical analysis of multiple choice test and questionnaire data. McGill University, Montreal, Canada

See Also

qrs, irf, plot.irf

Author(s)

Ivailo Partchev