piplot {psychotools} | R Documentation |
Base graphics plotting function for person-item plot visualization of IRT models.
piplot(object, ref = NULL, items = NULL, xlim = NULL, names = NULL, labels = TRUE, main = "Person-Item Plot", xlab = "Latent trait", abbreviate = FALSE, cex.axis = 0.8, cex.text = 0.5, cex.points = 1.5, ...)
object |
a fitted model object of class
|
ref |
argument passed over to internal calls of
|
items |
character or numeric, specifying the items which should be visualized in the person-item plot. |
xlim |
numeric, specifying the x axis limits. |
names |
character, specifying labels for the items. |
labels |
logical, whether to draw the number of the threshold as text below the threshold. |
main |
character, specifying the overall title of the plot. |
xlab |
character, specifying the x axis labels. |
abbreviate |
logical or numeric, specifying whether object names are to be abbreviated. If numeric this controls the length of the abbreviation. |
cex.axis |
numeric, the magnification to be used for the axis
notation relative to the current setting of |
cex.text |
numeric, the magnification to be used for the symbols
relative to the current setting of |
cex.points |
numeric, the magnification to be used for the points
relative to the current setting of |
... |
further arguments passed to internal calls of
|
The person-item plot visualization illustrates the distribution of the person parameters against the absolute item threshold parameters under a certain data set and IRT model.
curveplot
, regionplot
,
profileplot
, infoplot
## Verbal aggression data data("VerbalAggression", package = "psychotools") ## Fit a partial credit model to VerbalAggression data pcmod <- pcmodel(VerbalAggression$resp) ## Create a person-item plot visualization of the fitted PCM plot(pcmod, type = "piplot") ## Just visualize the first six items plot(pcmod, type = "piplot", ref = 1:6)