plot.difORD: ICC plots for an object of '"difORD"' class.

In adelahladka/difNLR: DIF and DDF Detection by Non-Linear Regression Models

ICC plots for an object of "difORD" class.

Description

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

The characteristic curves (category probabilities) for an item specified in item argument are plotted. Plotted curves represent the best model. For cumulative logit model, also cumulative probabilities may be plotted.

Usage

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

Arguments

x	an object of "difORD" class.
item	numeric or character: either character "all" to apply for all converged items (default), or a vector of item names (column names of Data), or item identifiers (integers specifying the column number).
plot.type	character: which plot should be displayed for cumulative logit regression model. Either "category" (default) for category probabilities or "cumulative" for cumulative probabilities.
group.names	character: names of reference and focal group.
...	other generic parameters for plot() function.

Value

Returns list of objects of class "ggplot".

Author(s)

Adela Hladka (nee Drabinova)
Institute of Computer Science of the Czech Academy of Sciences
Faculty of Mathematics and Physics, Charles University
[e-mail]

Patricia Martinkova
Institute of Computer Science of the Czech Academy of Sciences
[e-mail]

See Also

difORD for DIF detection among ordinal data.
ggplot for general function to plot a "ggplot" object.

Examples

## Not run: 
# loading data
data(Anxiety, package = "ShinyItemAnalysis")
Data <- Anxiety[, paste0("R", 1:29)] # items
group <- Anxiety[, "gender"] # group membership variable

# testing both DIF effects with adjacent category logit model
(x <- difORD(Data, group, focal.name = 1, model = "adjacent"))

# graphical devices
plot(x, item = 6)
plot(x, item = "R6", group.names = c("Males", "Females"))

# testing both DIF effects with cumulative logit model
(x <- difORD(Data, group, focal.name = 1, model = "cumulative"))
plot(x, item = 7, plot.type = "cumulative")
plot(x, item = 7, plot.type = "category")

## End(Not run)

adelahladka/difNLR documentation built on Dec. 23, 2024, 2:20 a.m.