R/DistanceDistribution.R

In YunlongJiao/kernrank: Kernel Methods for Rank Data

#' Calculate the Kendall distance distribution in \code{N!} space
#' 
#' This function counts the number of fully-ordered vectors at each distance in
#' \code{N!} space.
#' 
#' 
#' @param N Integer value, greater than or equal to 3.
#' @return Table-like structure, where the names represent the distance from
#' the modal sequence of each sequence in \code{N!} space, 
#' and the values represent the number of sequences at that distance in the sequence space.
#' @author Erik Gregory
#' @export
#' @keywords Kendall Distance
#' @examples
#' ## Not run:
#' 
#' # DistanceDistribution(10)
#' 
#' ## End(Not run)
#' 
#' @note Taken directly from R CRAN package \href{https://cran.r-project.org/web/packages/RMallow/index.html}{RMallow}.
#' 

DistanceDistribution <- function(N = 3)
{
  if (N <= 4) {
  	out <- table(SeqDistribution(N))
  }
  else {
  	out <- table(SeqDistribution(4))
        i <- 4
	while (i < N) {
	   out <- NextTable(out, i)
	   i <- i + 1
	}
  	names(out) <- as.character(0:(length(out) - 1))
  }
  return(out)
}