R/simPC.R

In prefmod: Utilities to Fit Paired Comparison Models for Preferences

# simulates paired comparison data with given worth
# 2 response categories, no undecided category
#
simPC<-function(nobj,nobs,worth=NULL,seed=NULL,pr=FALSE)
{

   if(is.null(worth))
       worth<-runif(nobj)
   else if(length(worth)!=nobj)
       stop("length of worth is not equal to nobj\n")
   worth<-worth/sum(worth)
   if (pr)
     cat("used worth parameters are: ", worth, "\n")
   probs<-NULL
   for (j in 2:(nobj)){
     for (i in 1:(j-1)){
        probs<-c(probs,worth[i]/(worth[i]+worth[j]))
     }
   }
   ncomp<-choose(nobj,2)
   if(!is.null(seed)) set.seed(seed)
   data<-NULL
   for (i in 1:ncomp)
     data<-cbind(data,sample(c(1,-1),nobs,replace=TRUE,prob=c(probs[i],1-probs[i])))
   data.frame(data)
}