lordif (version 0.1-1)

plot.lordif: Plot method for lordif class

Description

plots diagnostic graphs for items identified as displaying DIF

Usage

## S3 method for class 'lordif':
plot(x, labels = c("Reference", "Focal"), ...)

Arguments

x

output from lordif

labels

labels for group levels, e.g., c("Male","Female")

...

extra graphical parameters

Details

Generates the following graphs IF there is one or more DIF items: 1. Trait Distributions - density graphs for groups 2. Item True Score Functions - true score functions by theta for groups 3. Differences in Item True Score Functions - unsigned differences 4. Item Response Functions - item response function for groups 5. Impact (Weighted by Density) - unsigned differences weighted by theta distributions for the focal group 6. Comparison of TCCs by group based on all items and DIF items 7. Impact on Theta Estimates - theta estimates by group before and after accounting for DIF Graphs 2-5 are generated for each DIF item Graphs 1, 6 and 7 are generated for the whole analysis

See Also

lordif

Examples

##run lordif first
##age.dif <- lordif(Anxiety[paste("R",1:29,sep="")],Anxiety$age)
##plot(age.dif,labels=c("Younger","Older"),cex=0.8,lwd=1)