R/dk_time.R

In markhogue/radsafer: Radiation Safety

#' Time to decay to target radioactivity.
#' @family decay corrections
#' @description Calculate time for a radionuclide to decay to a target activity.
#' @param half_life, Half-life. Units are arbitrary, but must match time past.
#' @param A0 The original activity, or related parameter.
#' @param A1 The target activity.
#' @return Time, in same units as half-life, to decay to target activity.
#' @examples
#' # A carbonaceous artifact has a C-14 measurement of 1 dpm per g pure carbon.
#' # The reference activity is 14 dpm per g pure carbon. How old is our sample?
#' dk_time(half_life = 5730, A0 = 14, A1 = 1)
#' @export
dk_time <- function(half_life, A0, A1) {
  if (!is.numeric(c(half_life, A0, A1))) {
    stop("All arguments must be a numbers.")
  }
  -half_life * log(A1 / A0) / log(2)
}