Convert an estimated mirt model to a data.frame

Given an estimated model from any of mirt's model fitting functions this function will convert the model parameters into the design data frame of starting values and other parameter characteristics (similar to using the pars = 'values' for obtaining starting values).

Usage

mod2values(x)

Arguments

x

an estimated model x from the mirt package

References

Chalmers, R., P. (2012). mirt: A Multidimensional Item Response Theory Package for the R Environment. Journal of Statistical Software, 48(6), 1-29. doi:10.18637/jss.v048.i06

See also

extract.mirt

Author

Phil Chalmers rphilip.chalmers@gmail.com

Examples

if (FALSE) { # \dontrun{
dat <- expand.table(LSAT7)
mod <- mirt(dat, "F=1-5
                  CONSTRAIN=(1-5, a1)")
values <- mod2values(mod)
values

# use the converted values as starting values in a new model, and reduce TOL
mod2 <- mirt(dat, 1, pars = values, TOL=1e-5)
coef(mod2, simplify=TRUE)

# use parameters on different dataset
mod3 <- mirt(expand.table(LSAT6), pars=values)
coef(mod3, simplify=TRUE)

# supports differing itemtypes on second model
sv <- mirt(Science, itemtype=c('graded', rep('gpcm', 3)), pars='values')
mod3 <- mirt(Science, pars = sv)  # itemtype omitted
coef(mod3, simplify=TRUE)$items
extract.mirt(mod3, 'itemtype')


} # }