plot.DIFtree function

Plotting of Item focussed Trees

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

## S3 method for class '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

Examples

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)
## End(Not run)

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

Author(s)

Moritz Berger moritz.berger@imbie.uni-bonn.de

http://www.imbie.uni-bonn.de/personen/dr-moritz-berger/