R/irtprob2.R

In czopluoglu/CopyDetect: Computing Response Similarity Indices for Multiple-Choice Tests

#'a small function to compute the probability for NRM
#'
#'@param ability ability parameter
#'
#'@param item.param NRM item parameter matrix
#'
#'@noRd

irtprob2 <- function(ability,item.param) {  
  
  prob <- matrix(nrow=nrow(item.param),ncol=ncol(item.param)/2)
  
  for(i in 1:nrow(prob)){
    ps <- c()
    for(j in 1:ncol(prob)){ps[j]=exp((item.param[i,j]*ability)+item.param[i,j+ncol(prob)])
    }
    prob[i,]=ps/sum(ps)
  }
  prob
}