R/plausible.value.draw.R

In miceadds: Some Additional Multiple Imputation Functions, Especially for 'mice'

## File Name: plausible.value.draw.R
## File Version: 0.15


plausible.value.draw <- function( data, X, beta0, sig0, b=b,
            a=rep(1, length(b) ), c=rep(0, length(b) ),
            theta.list=seq(-5,5,len=40), pvdraw=1 )
{
    # recode missings
    y <- data
    y[ is.na(data) ] <- 1
    respind <- 1 - is.na(data)
    sig0[ sig0 < 0] <- 0
    n <- nrow(y)
    # predicted values from lalent regression
    M.Regr <- ( X %*% beta0 )[,1]
    if (length(sig0) > 1){ SD.Regr <- sig0 } else { SD.Regr <- rep( sig0, n ) }
    # matrix of theta values
    thetaM <- outer( rep(1,n), theta.list )
    # compute density resulting from regression
    dens.Regr <- stats::dnorm( thetaM, mean=M.Regr, sd=SD.Regr )
    # conditional distribution of item responses
    dens.Resp <- matrix( 0, nrow=n, ncol=ncol(dens.Regr) )
    for (tt in seq(1, length(theta.list)) ){
    ptt <- outer( rep(1, n), c + (1-c)*stats::plogis( a * ( theta.list[tt] - b ) ) )
        dens.Resp[,tt] <- exp( rowSums( respind *y * log( ptt) + respind*(1-y) *
                                    log( 1-ptt)  ) )
    }
    dens.total <- dens.Resp * dens.Regr
    dens.total <- dens.total / rowSums( dens.total)
    theta.listM <- outer( rep(1,n), theta.list )
    # mean of individual posterior distribution
    EAP <- rowSums( theta.listM * dens.total )
    # SD of posterior distribution
    SD.Post <- sqrt( rowSums( theta.listM^2 * dens.total ) -  EAP^2 )
    # one draw of plausible values
    if (pvdraw==FALSE ){ pvdraw <- NULL } else {
        pvdraw <- matrix( stats::rnorm( n*pvdraw, mean=rep(EAP,each=pvdraw),
                        sd=rep(SD.Post,each=pvdraw) ), ncol=pvdraw, byrow=TRUE )
    }
    # results
    res <- list( posterior.density=dens.total, EAP=EAP, SE.EAP=SD.Post,
            plausible.value=pvdraw, M.Regr=M.Regr, SD.Regr=SD.Regr )
    return(res)
}