Dcenter.R

#' Function to compute double-centred distance matrices
#'
#' @param x is a vector containing the values of a variable
#'
#' @return Dcentered vactor for x
#'
#' @examples
#' Dcenter(c(1,2,3,4))
#'
#' @export

############################################################
### Function to compute double-centred distance matrices ###
############################################################

Dcenter <- function(x) {
  # x is a vector containing the values of a variable

  n <- length(x) # number of points in dimension of x

  # compute distance matrix a
  a <- outer(x, x, function(x1, x2) abs(x1 - x2))

  # normalise a
  ahat <- a - matrix(rowMeans(a), nrow = n, ncol = n) - matrix(colMeans(a), nrow = n, ncol = n, byrow = TRUE) + mean(a)

  #return(ahat[!upper.tri(ahat)])
  return(ahat)
}