nmode's Git Repositories - Rnaught/blob - R/WP_known.R

   1 #' WP method background function WP_known
   2 #'
   3 #' This is a background/internal function called by \code{WP}. It computes the maximum
   4 #' likelihood estimator of R0 assuming that the serial distribution is known and finite discrete.
   5 #'
   6 #' @param NT vector of case counts
   7 #' @param p discretized version of the serial distribution
   8 #' @return The function returns \code{Rhat}, the maximum likelihood estimator of R0.
   9 #'
  10 #' @export
  11 WP_known <- function(NT, p) {
  12     k <- length(p)
  13     TT <- length(NT) - 1
  14         mu_t <- rep(0, TT)
  15
  16     for (i in 1:TT) {
  17         Nt <- NT[i:max(1, i-k+1)]
  18         mu_t[i] <- sum(p[1:min(k, i)] * Nt)
  19     }
  20
  21     Rhat <- sum(NT[-1]) / sum(mu_t)
  22         return(Rhat)
  23 }