R/efftox_utility.R

In trialr: Clinical Trial Designs in 'rstan'

#' @title Get the utility of efficacy & toxicity probability pairs
#'
#' @description Get the utility of efficacy & toxicity probability pairs
#'
#' @param p p-index of EffTox utility contours. Use \code{efftox_solve_p}
#' @param eff0 Efficacy probability required when toxicity is impossible;
#' a number between 0 and 1
#' @param tox1 Toxicity probability permitted when efficacy is guaranteed;
#' a number between 0 and 1
#' @param prob_eff Probability of efficacy; number between 0 and 1
#' @param prob_tox Probability of toxicity; number between 0 and 1
#'
#' @return Utility value(s)
#'
#' @export
#'
#' @examples
#' p <- efftox_solve_p(0.5, 0.65, 0.7, 0.25)
#'
#' u <- efftox_utility(p, 0.5, 0.65, prob_eff = 0.7, prob_tox = 0.25)
#' round(u, 4) == 0
#'
#' u <- efftox_utility(p, 0.5, 0.65, prob_eff = c(0.6, 0.7, 0.8),
#'                     prob_tox = c(0.1, 0.2, 0.3))
#' round(u, 2) == c(0.04, 0.08, 0.12)
#'
#' @seealso \code{\link{efftox_solve_p}}
efftox_utility <- function(p, eff0, tox1, prob_eff, prob_tox) {
  a <- ((1 - prob_eff) / (1 - eff0))
  b <- prob_tox / tox1
  r = (a^p + b^p) ^ (1/p)
  return(1 - r)
}