R/loglikcush00.R

In CUB: A Class of Mixture Models for Ordinal Data

#' @title Log-likelihood function for a CUSH model without covariates
#' @aliases loglikcush00
#' @description Compute the log-likelihood function for a CUSH model 
#' without covariate for the given ordinal responses.
#' @usage loglikcush00(m,ordinal,delta,shelter)
#' @param m Number of ordinal categories
#' @param ordinal Vector of ordinal responses
#' @param delta Shelter parameter
#' @param shelter Category corresponding to the shelter choice
#' @seealso \code{\link{GEM}}
#' @keywords internal


loglikcush00<-function(m,ordinal,delta,shelter){
  
  if (is.factor(ordinal)){
    ordinal<-unclass(ordinal)
  }
  n<-length(ordinal);
  freq<-tabulate(ordinal,nbins=m)
  fc<-freq[shelter]/n
  loglik<-n*((1-fc)*log(1-delta)+fc*log(1+(m-1)*delta)-log(m))
  return(loglik)
}