Description Usage Arguments Details See Also Examples
Base graphics plotting function for response curve plot visualization of IRT models.
1 2 3 4 
object 
a fitted model object of class

ref 
argument passed over to internal calls of 
items 
character or numeric, specifying the items for which response curves should be visualized. 
names 
character, specifying labels for the items. 
layout 
matrix, specifying how the response curve plots of different items should be arranged. 
xlim, ylim 
numeric, specifying the x and y axis limits. 
col 
character, specifying the colors of the response curve lines. The
length of 
lty 
numeric, specifying the line type of the response curve lines. The
length of 
main 
character, specifying the overall title of the plot. 
xlab, ylab 
character, specifying the x and y axis labels. 
add 
logical. If 
... 
further arguments passed to internal calls of 
The response curve plot visualization illustrates the predicted probabilities as function of the ability parameter θ under a certain IRT model. This type of visualization is sometimes also called item/category operating curves or item/category characteristic curves.
regionplot
, profileplot
,
infoplot
, piplot
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27  ## Load Verbal Aggression data
data("VerbalAggression", package = "psychotools")
## Fit Rasch, rating scale and partial credit
## model to VerbalAggression data
rmmod < raschmodel(VerbalAggression$resp2)
rsmod < rsmodel(VerbalAggression$resp)
pcmod < pcmodel(VerbalAggression$resp)
## Curve plots of the dichotomous RM
plot(rmmod, type = "curves")
## Curve plots under the rating scale model
## for the first six items of the data set
plot(rsmod, type = "curves", items = 1:6)
## Curve plots under the partial credit model
## for the first six items of the data set
## with custom labels
plot(pcmod, type = "curves", items = 1:6,
names = paste("Item", 1:6))
## Compare the predicted probabilities under the rating
## scale model and the partial credit model for a single item
plot(rsmod, type = "curves", item = 1)
plot(pcmod, type = "curves", item = 1, lty = 2, add = TRUE)
legend(x = "topleft", y = 1.0, legend = c("RSM", "PCM"), lty = 1:2, bty = "n")

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