R/differences.R

In prefmod: Utilities to Fit Paired Comparison Models for Preferences

`differences` <-
function(in_mat){
################################################################
# calculate differences from non-paired comparison responses
# (i.e. ratings/Likert or rankings)
# Sinclair ordering: (1-2)(1-3)(2-3)(1-4)
################################################################

   ncomp <-get("ncomp",get("ENV", environment(patt.design)))
   nobj  <-get("nobj",get("ENV", environment(patt.design)))

   diffs<-matrix(c(0:0),nrow(in_mat),ncomp)
   col<-1
   for (j in 2:nobj) {
       for (i in 1:(j-1) ){
           diffs[, col]  <- in_mat[,i]-in_mat[,j]
           col <- col + 1
       }
   }
   diffs
}