plotCCC function

plotCCC

Creates a plot of an item characteristic curve (by response category). For a dichotomous item, this will yield a single curve, for polytomous items this will produce a curve for each response category. Note this is not for use with rout files. See the generic function plotRout for plotting rout files.

plotCCC(
  item,
  abilities,
  responses,
  weights = NULL,
  groups = NULL,
  range = c(-6, 6),
  by = 0.1,
  linetype = "bins",
  bins = 10,
  plotZero
)

Arguments

• item: A matrix of item parameters for a single item. Matrix should be of the form used in simplef
• abilities: A vector of doubles estimated person abilities.
• responses: A vector of integers giving the observed person responses to this item.
• weights: A vector of doubles of sampling weights.
• groups: A factor vector indicating groups.
• range: Lower and upper bounds to plot over (defaults to c(-6, 6)).
• by: A double. The increment to the sequence along range used to plot the model lines.
• linetype: A string. Should the empirical lines be based on "bins", or "regression". Defaults to "bins"
• bins: If linetype is "bins", how many bins should be used to chunk the empirical lines? defaults to 10. Ignored otherwise.
• plotZero: Should the zero category be plotted? Defaults to FALSE when item is dichotomous and TRUE otherwise.

Returns

A ggplot2 object.

Examples

myRout <- ConQuestRout()
myPlot <- plotRout(myRout)
## Not run:

# if you run the above example you will have an ICC plot in the object `myPlot`.
plot(myPlot)
## End(Not run)