R/IRT.se.din.R

In CDM: Cognitive Diagnosis Modeling

## File Name: IRT.se.din.R
## File Version: 0.12

#########################################################################
IRT.se.din <- function( object, extended=FALSE, parm=NULL,
        level=.95, infomat=FALSE, ind.item.skillprobs=TRUE,
        ind.item=FALSE, diagcov=FALSE, h=.001, ... )
{
    if ( ! missing( parm) ){
        partable <- object$partable
        g1 <- parm %in% partable$parnames
        if ( mean(g1) < 1 ){
            stop("Not all requested parameters in parameter table!\n")
        }
    }
    # variance covariance matrix
    v1 <- vcov( object, extended=extended, infomat=FALSE,ind.item.skillprobs=ind.item.skillprobs,
                ind.item=ind.item, diagcov=diagcov, h=h,...)
    # confidence intervals
    res <- data.frame( "parameter"=names(attr( v1, "coef")) )
    res$est <- attr(v1,"coef")
    res$se <- sqrt( diag(v1)  )

    level1 <-  round( 100*( 1  - level ) / 2, 1 )
    quant1 <- abs( stats::qnorm( ( 1-level) / 2) )
    res[, paste0( level1, " %" ) ] <- res$est - quant1*res$se
    res[, paste0( 100-level1, " %" ) ] <- res$est + quant1*res$se

partable <- object$partable
    ind1 <- match( res$parameter, partable$parnames )
    vars1 <- c("partype", "parindex" )
    res <- cbind( partable[ ind1, vars1 ], res )
    vars2 <- c( "item", "item.name", "skillclass", "fixed","free",
                "rule", "totindex"  )
    res <- cbind( res, partable[ ind1, vars2 ])
    return(res)
}