mirt (version 1.1)

imputeMissing: Imputing plausible data for missing values

Description

Given an estimated model from any of mirt's model fitting functions and an estimate of the latent trait, impute plausible missing data values. Returns the original data in a data.frame without any NA values. If a list of Theta values is supplied then a list of complete datasets is returned instead.

Usage

imputeMissing(x, Theta, ...)

Arguments

x

an estimated model x from the mirt package

Theta

a matrix containing the estimates of the latent trait scores (e.g., via fscores). Can also be a list input containing different estimates for Theta (e.g., plausible value draws)

...

additional arguments to pass

Examples

dat <- expand.table(LSAT7)
(original <- mirt(dat, 1))
NAperson <- sample(1:nrow(dat), 20, replace = TRUE)
NAitem <- sample(1:ncol(dat), 20, replace = TRUE)
for(i in 1:20)
    dat[NAperson[i], NAitem[i]] <- NA
(mod <- mirt(dat, 1))
scores <- fscores(mod, method = 'MAP', full.scores = TRUE)

#re-estimate imputed dataset (good to do this multiple times and average over)
fulldata <- imputeMissing(mod, scores)
(fullmod <- mirt(fulldata, 1))

#with multipleGroup
group <- rep(c('group1', 'group2'), each=500)
mod2 <- multipleGroup(dat, 1, group, TOL=1e-2)
fs <- fscores(mod2, full.scores=TRUE)
fulldata2 <- imputeMissing(mod2, fs)

#supply list of plausible value estimates (the best approach when Theta's are imprecise)
pv <- fscores(mod, plausible.draws = 5)
fulldata_list <- imputeMissing(mod, pv)
str(fulldata_list)