R/calcFE.R

In rmsharp/nprcmanager: Genetic Tools for Colony Management

#' Calculates founder Equivalents
#'
## Copyright(c) 2017-2020 R. Mark Sharp
## This file is part of nprcgenekeepr
#' Part of the Genetic Value Analysis
#'
#' It is assumed that the pedigree has no partial parentage
#'
#' @return The founder equivalents \code{FE = 1 / sum(p ^ 2)}, where \code{p}
#' is average number of descendants and \code{r} is the mean number of founder
#' alleles retained in the gene dropping experiment.
#'
#' @examples
#' \donttest{
#' ## Example from Analysis of Founder Representation in Pedigrees: Founder
#' ## Equivalents and Founder Genome Equivalents.
#' ## Zoo Biology 8:111-123, (1989) by Robert C. Lacy
#' library(nprcgenekeepr)
#' ped <- data.frame(
#' id = c("A", "B", "C", "D", "E", "F", "G"),
#' sire = c(NA, NA, "A", "A", NA, "D", "D"),
#' dam = c(NA, NA, "B", "B", NA, "E", "E"),
#' stringsAsFactors = FALSE
#' )
#' ped["gen"] <- findGeneration(ped$id, ped$sire, ped$dam)
#' ped$population <- getGVPopulation(ped, NULL)
#' pedFactors <- data.frame(
#'   id = c("A", "B", "C", "D", "E", "F", "G"),
#'   sire = c(NA, NA, "A", "A", NA, "D", "D"),
#'   dam = c(NA, NA, "B", "B", NA, "E", "E"),
#'   stringsAsFactors = TRUE
#' )
#' pedFactors["gen"] <- findGeneration(pedFactors$id, pedFactors$sire,
#'                                     pedFactors$dam)
#' pedFactors$population <- getGVPopulation(pedFactors, NULL)
#' fe <- calcFE(ped)
#' feFactors <- calcFE(pedFactors)
#' }
#'
#' @param ped the pedigree information in datatable format.  Pedigree
#' (req. fields: id, sire, dam, gen, population).
#' @export
calcFE <- function(ped) {
  ped <- toCharacter(ped, headers = c("id", "sire", "dam"))
  founders <- ped$id[is.na(ped$sire) & is.na(ped$dam)]
  ## UID.founders <- founders[grepl("^U", founders, ignore.case = TRUE)]
  ## UID.founders is not used; It may be a mistake, but it could be vestiges of
  ## something planned that was not done.
  descendants <- ped$id[!(ped$id %in% founders)]

  d <- matrix(0, nrow = length(descendants), ncol = length(founders))
  colnames(d) <- founders
  rownames(d) <- descendants

  founderMatrix <- diag(length(founders))
  colnames(founderMatrix) <- rownames(founderMatrix) <- founders

  d <- rbind(founderMatrix, d)
  founderMatrix <- NULL
  ## Note: skips generation 0.
  ## The references inside matrix d do not work if ped$sire and ped$dam and
  ## thus gen$sire and gen$dam are factors. See test_calcFE.R
  for (i in seq_len(max(ped$gen))) {
    gen <- ped[(ped$gen == i), ]

    for (j in seq_len(nrow(gen))) {
      ego <- gen$id[j]
      sire <- gen$sire[j]
      dam <- gen$dam[j]
      d[ego, ] <- (d[sire, ] + d[dam, ]) / 2
    }
  }

  currentDesc <- ped$id[ped$population & !(ped$id %in% founders)]
  d <- d[currentDesc, ]
  p <- colMeans(d)

  return(1 / sum(p ^ 2))
}