Plotting of Item focussed Trees

Share:

Description

Visualization of trees for items with DIF identified by item focussed recursive partitioning based on the Rasch Model or the Logistic Regression Approach for DIF detection.

Usage

1
2
3
## 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" model only one tree of item difficulties 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 given 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

Author(s)

Moritz Berger <moritz.berger@stat.uni-muenchen.de>
http://www.statistik.lmu.de/~mberger/

References

Berger, Moritz and Tutz, Gerhard (2015): Detection of Uniform and Non-Uniform Differential Item Functioning by Item Focussed Trees, Cornell University Library, arXiv:1511.07178

Tutz, Gerhard and Berger, Moritz (2015): Item Focused Trees for the Identification of Items in Differential Item Functioning, Psychometrika, published online, DOI: 10.1007/s11336-015-9488-3

See Also

DIFtree, predict.DIFtree, summary.DIFtree

Examples

 1
 2
 3
 4
 5
 6
 7
 8
 9
10
11
12
data(data_sim)
 
Y <- data_sim[,1]
X <- data_sim[,-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)