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 #'
   9 #' @return The function returns the maximum likelihood estimator of R0.
  10 #'
  11 #' @keywords internal
  12 WP_known <- function(NT, p) {
  13     k <- length(p)
  14     TT <- length(NT) - 1
  15         mu_t <- rep(0, TT)
  16
  17     for (i in 1:TT) {
  18         Nt <- NT[i:max(1, i-k+1)]
  19         mu_t[i] <- sum(p[1:min(k, i)] * Nt)
  20     }
  21
  22     Rhat <- sum(NT[-1]) / sum(mu_t)
  23         return(Rhat)
  24 }