R/annualGrowthRateCalculator.R

In bcgov/BCForestGroundSample: BC forest ground sample compilation

#' Calculate annual growth rate
#'
#'
#' @description This function is to calcualte annual growth rate.
#'
#' @param boredDiameter numeric, Diameter at bored height in cm.
#' @param growthIncrement numeric, Growth increment in mm over a time period.
#' @param growthYear numeric, Number of years over which growth increment is measured.
#' @param barkThickness numeric, Bark thickness in mm. If missing, 0.05 will be used.
#'
#'
#' @return Calculated annual growth rate.
#'
#' @importFrom data.table ':='
#'
#'
#' @export
#' @docType methods
#' @rdname annualGrowthRateCalculator
#'
#' @author Yong Luo
annualGrowthRateCalculator<- function(boredDiameter, growthIncrement,
                                      growthYear, barkThickness){
  worktable <- data.table(uniObs = 1:length(boredDiameter),
                          boredDiameter,
                          barkThickness,
                          growthIncrement,
                          growthYear)
  if(nrow(worktable[is.na(barkThickness)]) > 0){
    worktable[is.na(barkThickness), barkThickness := 0.05]
    warning("Bark thickness is missing, 0.05 was used.")
  }
  if(nrow(worktable[barkThickness < 0 | growthIncrement < 0,]) > 0){
    stop("Bark thickness and growth increment must be positive values.")
  }
  worktable[, radius := boredDiameter/2-barkThickness/10]
  worktable[, R := radius - growthIncrement/10]
  worktable[R > -0.001, R := abs(R)]
  worktable[R > 0 & growthIncrement > 0, growthRate := exp(log((radius^2)/(R^2))/growthYear) - 1]
  return(worktable[order(uniObs),]$growthRate)
}