R/group_sizes.R

In netseg: Measures of Network Segregation and Homophily

#' Computing group sizes from square mixing matrices
#'
#' [group_sizes()] recomputes group sizes from a full mixing matrix. This is
#' only limited to square (single-attribute) mixing matrices.
#'
#' @param mm numeric array with \code{dim} of \eqn{(k, k, 2)} for some \eqn{k}
#' @param directed logical, whether network is directed
#' @param loops logical, whether loops are allowed
#'
#' @return
#' A numeric vector of group sizes
#'
#' @export

group_sizes <- function(mm, directed=TRUE, loops=FALSE)
{
  # Works only for square full mixing matrices
  dims <- dim(mm)
  stopifnot( dims[1] == dims[2] )
  stopifnot( dims[3] == 2 )
  eamargin <- apply(mm, 1:2, sum)
  if(directed)
  {
    if(loops)
    {
      gsizes <- sqrt(diag(eamargin))
    } else
    {
      gsizes <- 0.5 * (1 + sqrt(1 + 4*diag(eamargin)))
    }
  } else
  {
    gsizes <- 0.5 * (1 + sqrt(1 + 8*diag(eamargin)))
  }
  gsizes
}