R/get_collisions_basic.R

In HiDef-Aerial-Surveying/stochLAB: Stochastic Collision Risk Model

#' Get expected collisions based on the basic model
#'
#' Provides the number of collisions expected to occur by month. The basic model
#' assumes a uniform distribution of bird flights at risk height (i.e. between
#' min and max rotor height).
#'
#' @param n_transits A numeric vector, the estimated number of bird flights crossing
#'   the rotors of the wind farm at each time period.
#' @param avg_prob_coll A numeric value, the average probability of collision for a single bird
#'   transit through a rotor, assuming no avoidance action (\eqn{p_{average}}).
#' @param mth_prop_oper A numeric vector, the proportion of time during which
#'   turbines are operational per month.
#' @param avoidance_rate A numeric value within the interval \eqn{[0, 1]}. The
#'   avoidance rate, expressing the probability that a bird flying on a
#'   collision course with a turbine will take evading action to avoid collision.
#' @param lac_factor A numerical value, the large array correction factor.
#'   Defaults to 1, meaning large array correction is not applicable.
#'
#' @return A numeric vector. The expected number of collisions at each time
#'   periods
#' @examples
#' turb_oper <- data.frame(
#'  month = month.abb,
#'  prop_oper = runif(12,0.5,0.8)
#'  )
#'  mth_oper_month <- turb_oper$prop_oper
#'
#'  flux_factor <- get_flux_factor(
#'    n_turbines = 100,
#'    rotor_radius = 120,
#'    flight_speed = 13.1,
#'    bird_dens = c(1.19,0.85,1.05,1.45,1.41,1.45,1.12,1.45,0.93,0.902,1.06,1.23),
#'    daynight_hrs = Day_Length(52),
#'    noct_activity = 0.5
#'  )
#'
#'  prop_crh_surv <- 0.13
#'
#'  n_transits_opt1 <- flux_factor * prop_crh_surv
#'
#'  get_collisions_basic(
#'    n_transits = n_transits_opt1,
#'    avg_prob_coll = 0.1494609,
#'    mth_prop_oper = mth_oper_month,
#'    avoidance_rate = 0.989,
#'    lac_factor = 0.9998287
#'  )
#'
#' @export
get_collisions_basic <- function(n_transits,
                                 avg_prob_coll,
                                 mth_prop_oper,
                                 avoidance_rate,
                                 lac_factor = 1){

  if(length(n_transits) != length(mth_prop_oper)){
    stop("Numeric vectors `n_transits` and `mth_prop_oper` must be of
         equal length", call. = FALSE)
  }

  n_transits * avg_prob_coll * mth_prop_oper *
    (1 - avoidance_rate) * lac_factor
}