ICC plots for an object of "ddfMLR" class.

Plot method for an object of "ddfMLR" class using ggplot2.

The characteristic curves for an item specified in item argument are plotted. Plotted curves represent the best model.

Usage

# S3 method for class 'ddfMLR'
plot(x, item = "all", group.names, ...)

Arguments

x

an object of "ddfMLR" class.

item

numeric or character: either character "all" to apply for all items (default), or a vector of item names (column names of Data), or item identifiers (integers specifying the column number).

group.names

character: names of reference and focal group.

...

other generic parameters for plot() function.

Value

Returns list of objects of class "ggplot".

See also

ddfMLR for DDF detection.
ggplot for general function to plot a "ggplot" object.

Author

Adela Hladka (nee Drabinova)
Institute of Computer Science of the Czech Academy of Sciences
Faculty of Mathematics and Physics, Charles University
hladka@cs.cas.cz

Patricia Martinkova
Institute of Computer Science of the Czech Academy of Sciences
martinkova@cs.cas.cz

Examples

if (FALSE) { # \dontrun{
# loading data
data(GMATtest, GMATkey)
Data <- GMATtest[, 1:20] # items
group <- GMATtest[, "group"] # group membership variable
key <- GMATkey # correct answers

# testing both DDF effects
(x <- ddfMLR(Data, group, focal.name = 1, key))

# graphical devices
plot(x, item = "Item1", group.names = c("Group 1", "Group 2"))
plot(x, item = x$DDFitems)
plot(x, item = c(3, 1, 5))
} # }