DIFtree (version 3.1.6)

plot.DIFtree: Plotting of Item focussed Trees

Description

Visualization of trees for items with DIF identified by item focussed recursive partitioning in dichotomous or polytomous items.

Usage

# S3 method for DIFtree
plot(x, item, component = "intercept", cex.lines = 2,
  cex.branches = 1, cex.coefs = 1, cex.main = 1, title = NULL, ...)

Arguments

x

Object of class DIFtree

item

Number of the item, for which the tree shall be plotted

component

Component of the model for which the tree shall be plotted; can be "intercept" or "slope". For "Rasch" and "PCM" only one tree of item parameters is available for each DIF item and therefore component will be ignored.

cex.lines

Width of branches of the tree

cex.branches

Size of the labels of branches of the tree

cex.coefs

Size of coefficients in the terminal nodes of the tree

cex.main

Size of the title of the tree

title

Optional title, which is added to the tree; if title=NULL the title is the number of the plotted item.

...

Further arguments passed to or from other methods

References

Berger, Moritz and Tutz, Gerhard (2016): Detection of Uniform and Non-Uniform Differential Item Functioning by Item Focussed Trees, Journal of Educational and Behavioral Statistics 41(6), 559-592.

Bollmann, Stella, Berger, Moritz & Tutz, Gerhard (2018): Item-Focussed Trees for the Detection of Differential Item Functioning in Partial Credit Models, Educational and Psychological Measurement 78(5), 781-804.

Tutz, Gerhard and Berger, Moritz (2016): Item focussed Trees for the Identification of Items in Differential Item Functioning, Psychometrika 81(3), 727-750.

See Also

DIFtree, predict.DIFtree, summary.DIFtree

Examples

# NOT RUN {
data(data_sim_Rasch)
 
Y <- data_sim_Rasch[,1]
X <- data_sim_Rasch[,-1]
 
# }
# NOT RUN {
 
mod <- DIFtree(Y=Y,X=X,model="Logistic",type="udif",alpha=0.05,nperm=1000,trace=TRUE)
 
plot(mod,item=1)
# }