R/potentially_effective_spores.R

In ascotraceR: Simulate the Spread of Ascochyta Blight in Chickpea

#' Estimate the potentially infective spores
#'
#' @param spores_per_gp_per_wet_hour estimated number of spores produced in one
#'   hour from a single chickpea growing point
#' @param max_interception_probability double with length of one; Estimates the
#'   maximum interception probability using the `spore_interception_parameter`,
#'   see function `interception_probability()`
#' @param paddock_infected_gp integer value giving number of sporulating growing
#'   points per paddock
#'
#' @return a double providing the potentially infective spores at the
#'   `paddock_infected_gp` coordinates
#' @noRd
#' @examples
#' # default parameter of the model
#' potentially_effective_spores(spores_per_gp_per_wet_hour = 0.22,
#'   max_interception_probability = 1,
#'   paddock_infected_gp = 100) # No. of infected growing points at coordinates
potentially_effective_spores <- function(spores_per_gp_per_wet_hour,
                                         max_interception_probability,
                                         paddock_infected_gp) {
  if (paddock_infected_gp <= 0) {
    return(0)
  } else{
    expected_effective_spores <-
      spores_per_gp_per_wet_hour *
      max_interception_probability *
      paddock_infected_gp

    if (expected_effective_spores < 0) {
      stop(
        call. = FALSE,
        "Function 'potentially_effective_spores() returning negative values\n",
        "Check parameters `spores_per_gp_per_wet_hour` and",
        "`max_interception_probability`."
      )
    } else{
      p_e_s <-
        stats::rpois(1, expected_effective_spores)

      return(p_e_s)
    }
  }
}