mirt (version 1.42)

read.mirt: Translate mirt parameters into suitable structure for plink package

Description

This function exports item parameters from the mirt package to the plink package.

Usage

read.mirt(x, as.irt.pars = TRUE, ...)

Arguments

x

a single object (or list of objects) returned from mirt, bfactor, or a single object returned by multipleGroup

as.irt.pars

if TRUE, the parameters will be output as an irt.pars object

...

additional arguments to be passed to coef()

Author

Phil Chalmers

Examples

if (FALSE) {

## unidimensional
library(plink)

data <- expand.table(LSAT7)
(mod1 <- mirt(data, 1))
plinkpars <- read.mirt(mod1)
plot(plinkpars)
plot(mod1, type = 'trace')

# graded
mod2 <- mirt(Science, 1)
plinkpars <- read.mirt(mod2)
plot(plinkpars)
plot(mod2, type = 'trace')

# gpcm
mod3 <- mirt(Science, 1, itemtype = 'gpcm')
plinkpars <- read.mirt(mod3)
plot(plinkpars)
plot(mod3, type = 'trace')

# nominal
mod4 <- mirt(Science, 1, itemtype = 'nominal')
plinkpars <- read.mirt(mod4)
plot(plinkpars)
plot(mod4, type = 'trace')

## multidimensional

data <- expand.table(LSAT7)
(mod1 <- mirt(data, 2))
plinkpars <- read.mirt(mod1)
plinkpars
plot(plinkpars)
plot(mod1, type = 'trace')

cmod <- mirt.model('
   F1 = 1,4,5
   F2 = 2-4')
model <- mirt(data, cmod)
plot(read.mirt(model))
itemplot(model, 1)

# graded
mod2 <- mirt(Science, 2)
plinkpars <- read.mirt(mod2)
plinkpars
plot(plinkpars)
plot(mod2, type = 'trace')

### multiple group equating example
set.seed(1234)
dat <- expand.table(LSAT7)
group <- sample(c('g1', 'g2'), nrow(dat), TRUE)
dat1 <- dat[group == 'g1', ]
dat2 <- dat[group == 'g2', ]
mod1 <- mirt(dat1, 1)
mod2 <- mirt(dat2, 1)

# convert and combine pars
plinkMG <- read.mirt(list(g1=mod1, g2=mod2))

# equivalently:
# mod <- multipleGroup(dat, 1, group)
# plinkMG <- read.mirt(mod)

combine <- matrix(1:5, 5, 2)
comb <- combine.pars(plinkMG, combine, grp.names=unique(group))
out <- plink(comb, rescale="SL")
equate(out)
equate(out, method = 'OSE')

}