R/nIndividuals.R

In bogdanoancea/aggregation: R package for aggregation of device numbers into population number

#' @title Computes the number of individuals as a sum of multinomial varibales.
#'
#' @description Computes the number of individuals as a sum of multinomial
#'   varibales. It is an internal function that is called during the process of
#'   generating the Poisson multinomial distributed random values. This function
#'   cannot be directly called by the users.
#'
#' @param categories a list of categories in the form \code{region-devCount}.
#'
#' @return The sum of the multinomial variates.
#' @keywords internal
#' @import data.table
#' @export
nIndividuals <- function(categories){

  catPerDevice <- Reduce(rbind, lapply(as.character(categories), function(str) {

    as.numeric(strsplit(str, split = '-')[[1]])
  }))
  nDev <- length(categories)
  cells <- sort(unique(catPerDevice[, 1]))
  nCells <- max(cells)
  output <- numeric(nCells)
  names(output) <- cells
  for (dev_index in 1:nDev){

    cell <- catPerDevice[dev_index, 1]
    devCount <- catPerDevice[dev_index, 2]
    tempVec <- numeric(nCells)
    tempVec[cell] <- devCount
    output <- output + tempVec
  }

  return(output)
}