```
#' 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)
}
```

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