The equateIRT package computes:
Load the package equateIRT and the data
Estimate a two parameter logistic model for 5 data sets with the R package mirt
library("mirt")
m1 <- mirt(data2pl[[1]], SE = TRUE)
m2 <- mirt(data2pl[[2]], SE = TRUE)
m3 <- mirt(data2pl[[3]], SE = TRUE)
m4 <- mirt(data2pl[[4]], SE = TRUE)
m5 <- mirt(data2pl[[5]], SE = TRUE)
Create an object of class modIRT
(since package versione
2.5.0 it is possible to skip the import.mirt function)
mlist<- list(m1, m2, m3, m4, m5)
test <- paste("test", 1:5, sep = "")
mod2pl <- modIRT(est.mods = mlist, names = test, display = FALSE)
coef(mod2pl$test1)[1:5]
## Dffclt.I1 Dffclt.I2 Dffclt.I3 Dffclt.I4 Dffclt.I5
## 0.058224616 0.028019255 0.073234265 0.415936521 -0.006686047
The linkage plan
## [,1] [,2] [,3] [,4] [,5]
## [1,] 20 10 0 0 10
## [2,] 10 20 10 0 0
## [3,] 0 10 20 10 0
## [4,] 0 0 10 20 10
## [5,] 10 0 0 10 20
A graphic of the linkage plan with package sna
library(sna)
par(mar=c(0, 0, 0, 0))
set.seed(6)
gplot(lplan, displaylabels = TRUE, vertex.sides = 4, vertex.cex = 5, vertex.rot =45, usearrows = FALSE, label.pos = 5, label.cex = 1, vertex.col = 0)