Homebrew: R function to adjust hydrometer gravity reading

adjustHydrometer.R

adjustHydrometer <- function(SG = 1010, 
                             temp = 25,
                             calibTemp = 20,
                             unit = "C") {
  #initial argument checks
  if(!is.numeric(SG))
    stop("Argument \"SG\" must be numeric", call. = FALSE)
  if(!is.numeric(temp))
    stop("Argument \"temp\" must be numeric", call. = FALSE)
  if(!is.numeric(calibTemp))
    stop("Argument \"calibTemp\" must be numeric", call. = FALSE)
  if(length(calibTemp) != 1)
    stop("Calibration temperature must be a single value", call. = FALSE)
  if(!is.character(unit))
    stop("Argument \"unit\" must be character", call. = FALSE)
  if(!tolower(unit) %in% c("f", "c"))
    stop("Unit must be either \"F\" (for fahrenheit) or \"C\" (for celcius)", call. = FALSE)
  
  #formula from http://www.musther.net/vinocalc.html
  #formula is for temperatures in fahrenheit only, range: 0-60C 
  if(tolower(unit) == "c") {
    temp <- temp*1.8+32
    calibTemp <- calibTemp*1.8+32
  }
  CSG <- SG * ((1.00130346 - (0.000134722124 * temp) + (0.00000204052596 * temp^2) - (0.00000000232820948 * temp^3)) /
                 (1.00130346 - (0.000134722124 * calibTemp) + (0.00000204052596 * calibTemp^2) - (0.00000000232820948 * calibTemp^3)))
  return(CSG)
}