R/categoryMeasure.R

In changxiulee/BayesianRasch: Bayesian Rasch Modeling

#' categoryMeasure
#'
#' For response category analysis, for each category, get the theta estimated for subject that
#' choose the category and average them
#'
#' Reference
#' Linacre, J. M. (2002). Optimizing rating scale category effectiveness. Journal of applied measurement, 3(1), 85-106.
#' Linacre, J. M., & Wright, B. D. (2000). Winsteps. URL: http://www. winsteps. com/index. html
#'
#' @param obj Any model in the package
#' @export categoryMeasure

categoryMeasure = function (obj) {
  if(obj$DIF == TRUE){
    show("This is not available for DIF object")
  }else{
    item = obj$item
    data = obj$data[,item]
    if(min(apply(data, 2, min,na.rm = TRUE)) == 0){data = data + 1}
    theta.v = theta(obj)[,3]
    beta.v = beta(obj)[,3]
    K = apply(data, 2, max,na.rm = TRUE)
    out = matrix(NA,length(item), max(K))
    rownames(out) = item
    colnames(out) = 1:max(K)

    for(i in 1:length(item)){
      m = cbind(data[,i], theta.v - beta.v)
      m = m[order(m[,1]),]
      for(j in 1:K[i]){out[i,j]= mean(m[m[,1] == j, ], na.rm = TRUE)}
    }
    out
  }
}