## File Name: itemfit_sx2_calc_scoredistribution_R.R
## File Version: 0.04
##########################################################################
# calculate distribution of sum score
itemfit_sx2_calc_scoredistribution_R <- function( pjk )
{
# pjk .... [ TP, I, 2 ] ... [ theta points, items, 2 categories ]
P1 <- pjk[,,2]
Q1 <- pjk[,,1]
TP <- nrow(P1)
I <- ncol(P1)
score <- seq( 0, I, 1 )
scoredistribution <- matrix(NA, TP, I+1 )
scoredistribution[,1] <- Q1[,1]
scoredistribution[,2] <- P1[,1]
for (ii in 2:I){
scoredistribution0 <- scoredistribution
scoredistribution[,ii+1] <- P1[,ii] * scoredistribution0[,ii]
for (kk in seq( 0, ii - 2, 1 ) ){
scoredistribution[,ii-kk] <- Q1[,ii] * scoredistribution0[,ii-kk] +
P1[,ii] * scoredistribution0[,ii-kk-1]
}
scoredistribution[,1] <- Q1[,ii] * scoredistribution0[,1]
}
return(scoredistribution)
}
##############################################################################
.calc.scoredistribution.cdm <- itemfit_sx2_calc_scoredistribution_R
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