R/tam_mml_mfr_inits_xsi.R

In alexanderrobitzsch/TAM: Test Analysis Modules

## File Name: tam_mml_mfr_inits_xsi.R
## File Version: 0.09

tam_mml_mfr_inits_xsi <- function( gresp.noStep.ind, col.index, cA, pweights,
        xsi, xsi.start0, resp, A, xsi.inits, xsi.fixed, ItemScore, est.xsi.index, addnumb=.5 )
{
    # starting values for xsi
    gresp.ind.tmp <- gresp.noStep.ind[, col.index  ]
    ItemMax <- crossprod(gresp.ind.tmp %*% cA, pweights )
    ItemMax <- as.vector( t( colSums( gresp.ind.tmp * pweights ) ) %*% cA )

    xsi[est.xsi.index] <- - log(abs(( ItemScore[est.xsi.index]+addnumb)/
                        (ItemMax[est.xsi.index]-ItemScore[est.xsi.index]+addnumb) ) )
    # starting values of zero
    if( xsi.start0==1){
        xsi <- 0*xsi
    }
    if( xsi.start0==2){
        ind1 <- which( dimnames(A)[[3]] %in% colnames(resp) )
        ind2 <- which( dimnames(A)[[3]] %in% paste0( "step",1:9) )
        ind3 <- setdiff( seq(1,length(xsi) ), union(ind1,ind2) )
        xsi[ind3] <- 0
    }

    #log of odds ratio of raw scores
    xsi[ is.na(xsi) ] <- 0
    if ( ! is.null(xsi.inits) ){
        xsi[ xsi.inits[,1] ] <- xsi.inits[,2]
    }
    if ( ! is.null(xsi.fixed) ){
        xsi[ xsi.fixed[,1] ] <- xsi.fixed[,2]
    }
    #--- OUTPUT
    res <- list(xsi=xsi, ItemMax=ItemMax)
    return(res)
}