R/convert.distance.R

In EricArcher/swfscMisc: Miscellaneous Functions for Southwest Fisheries Science Center

#' @title Distance Conversion
#' @description Convert distances between kilometers, nautical miles, and statute miles.
#' 
#' @param x numeric. The distance to be converted.
#' @param from,to character. Units to convert from and to. Can be "km" (kilometers), 
#'   "nm" (nautical miles), or "mi" (statute miles), or any partial match 
#'   thereof (case sensitive).
#' 
#' @author Eric Archer \email{eric.archer@@noaa.gov}
#' 
#' @export
#' 
convert.distance <- function(x, from = c("nm", "km", "mi"), to = c("km", "nm", "mi")) {
  from <- match.arg(from)
  to <- match.arg(to)
  
  x <- switch(from,
    km = x,
    nm = x * 1.852,
    mi = x * 1.609344,
    NA
  )
  
  result <- switch(to,
    km = x,
    nm = x / 1.852,
    mi = x / 1.609344,
    NA
  )
  
  as.numeric(result)
}