R/select_max.R

In bobdouma/kappa_multinomial: Evaluate the performance of probabilistic multinomial models

##'   
##' @title select maximum
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##' @description This function select the class with highest probability in a sample. If multiple classes have the same heighest probability then one is randomly chosen
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##' @param x a vector with sample predictions: the elements represent the classes of outcomes. 
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##' @return returns a vector with the following elements: 
##' \itemize{
##' \item{y}
##' }
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##' @details helper function for the tutorial
##' @author Bob Douma
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##' @references 
##' NULL
##' @seealso 
##' NULL
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##' @examples 
##' library(gtools)
##' pred = rdirichlet(100, c(0.1,0.1,0.5,0.5)) # generate multinomial probabilties with four classes
##' pred.bin = multinomialperform:::prob_to_binary(pred)
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##' 
##' 
# this function converts multinomial probability distribution to presence/absence. If multiple classes are predicted with the same maximum probability one class is chosen.

select_max <- function(x){
  t.f = x>=max(x)
  if (length(x[t.f])>1){
    y = rep(0,length=length(x))
    seq.1 = c(1:length(x))
    index = sample(seq.1[t.f],1)
    y[index] = 1
  } else  {
    y = ifelse(x>=max(x),1,0)  
  }
  return(y)
}