R/get.tte.post.r

In GNGTools: Tools for Go/No-Go Decision-Making Framework

#' @title Get posterior parameters for two-sample time to event case using normal approximation to log(HR) - expand.grid
#' @description Returns the parameters of the posterior distribution in the case of normal approximation to hazard ratio
#' @param m.con.prior prior number of events on control
#' @param m.trt.prior prior number of events on treatment
#' @param HR.prior Prior Hazard ratio
#' @param ARatio Randomization ratio in current trial
#' @param HR.obs Observed HR in current trial
#' @param m.obs Total events in current trail
#' @return A data.frame is returned
#' @examples
#' my.tte.post <- get.tte.post()
#' my.tte.post
#' @export
get.tte.post <- function(m.con.prior=10, m.trt.prior=10, HR.prior=.7,
                         ARatio=1, HR.obs=.8, m.obs=50){
  expand.grid(m.con.prior=m.con.prior, m.trt.prior=m.trt.prior, HR.prior=HR.prior,
              ARatio=ARatio, HR.obs=HR.obs, m.obs=m.obs) %>%
    mutate(
      prior.mean = log(HR.prior),
      prior.sd = sqrt(4/(m.con.prior + m.trt.prior)),
      ARatio = 1/(1+ARatio),
      post.mean = (1 / m.con.prior + 1 / m.trt.prior) ^ (-1)/((1 / m.con.prior + 1 / m.trt.prior) ^ (-1) +
                                                                (1/(m.obs * ARatio*(1 - ARatio))) ^ (-1))*log(HR.prior) +    (1/(m.obs * ARatio*(1 - ARatio))) ^ (-1)/((1 / m.con.prior + 1 / m.trt.prior) ^ (-1) +  (1/(m.obs * ARatio*(1 - ARatio))) ^ (-1))*log(HR.obs),
      post.sd = sqrt(((1 / m.con.prior + 1 / m.trt.prior)*
                        (1/(m.obs * ARatio*(1 - ARatio))))/((1 / m.con.prior + 1 / m.trt.prior)+
                                                              (1/(m.obs * ARatio*(1 - ARatio))))))
}