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.
Usage
plotCCC(
item,
abilities,
responses,
weights = NULL,
groups = NULL,
range = c(-6, 6),
by = 0.1,
linetype = "bins",
bins = 10,
plotZero
)
Value
A ggplot2 object.
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.
myRout <- ConQuestRout()
myPlot <- plotRout(myRout)
if (FALSE) {
# if you run the above example you will have an ICC plot in the object `myPlot`.plot(myPlot)
}