R/elliptic.sim.adj.R

In jfrench/smerc: Statistical Methods for Regional Counts

#' Perform \code{elliptic.test} on simulated data
#'
#' \code{elliptic.sim} efficiently performs
#' \code{\link{elliptic.test}} on a simulated data set.  The
#' function is meant to be used internally by the
#' \code{\link{elliptic.test}} function, but is informative
#' for better understanding the implementation of the test.
#'
#' @inheritParams scan.sim
#' @param nn A list of nearest neighbors produced by
#'   \code{\link{elliptic.nn}}.
#' @inheritParams elliptic.test
#' @inheritParams stat.poisson.adj
#'
#' @return A vector with the maximum test statistic for each
#'   simulated data set.
#' @export
#'
#' @examples
#' data(nydf)
#' data(nyw)
#' coords <- with(nydf, cbind(longitude, latitude))
#' pop <- nydf$pop
#' enn <- elliptic.nn(coords, pop, ubpop = 0.5)
#' cases <- floor(nydf$cases)
#' ty <- sum(cases)
#' ex <- ty / sum(pop) * pop
#' yin <- nn.cumsum(enn$nn, cases)
#' ein <- nn.cumsum(enn$nn, ex)
#' logein <- log(ein)
#' logeout <- log(ty - ein)
#' pen <- elliptic.penalty(0.5, enn$shape_all)
#' tsim <- elliptic.sim.adj(
#'   nsim = 3, ex = ex,
#'   nn = enn$nn, ty = ty,
#'   logein = logein, logeout = logeout,
#'   a = 0.5, pen = pen
#' )
elliptic.sim.adj <- function(nsim = 1, ex, nn, ty, logein, logeout,
                             a, pen, min.cases = 2, cl = NULL) {
  # compute max test stat for nsim simulated data sets
  tsim <- pbapply::pblapply(seq_len(nsim), function(i) {
    # simulate new data
    ysim <- stats::rmultinom(1, size = ty, prob = ex)
    # compute test statistics for each zone
    yin <- nn.cumsum(nn, ysim)
    stat.poisson.adj(
      yin = yin,
      ty = ty,
      logein = logein, logeout = logeout,
      a = a, pen = pen,
      min.cases = min.cases,
      return.max = TRUE
    )
  }, cl = cl)
  unlist(tsim, use.names = FALSE)
}