Posterior probability that one group beats another

Estimates the posterior probability that a certain scalar summary of the survival distribution for group `a` is greater than the same summary for group `b`. Supported summaries are the median survival time, the survival probability at a fixed time `S(t_0)`, and the restricted mean survival time (RMST). The function works draw-by-draw on the posterior, so the probability is computed on the joint posterior of the two groups.

Usage

probability_superiority(
  fit,
  a,
  b,
  function_of = "median",
  newdata = NULL,
  times = NULL,
  tmax = NULL,
  ...
)

Arguments

fit

A fitted `exnex_surv` object.

a

An integer index (or group label) of the first group.

b

An integer index (or group label) of the second group.

function_of

Character; one of `"median"`, `"survival"` (alias `"S_t"`), or `"rmst"`. Selects which summary is compared.

newdata

Optional data frame with one row per group, used to fix covariates. If `NULL`, covariates are set to zero.

times

A scalar time at which to evaluate the survival function when `function_of = "survival"`.

tmax

A positive horizon when `function_of = "rmst"`.

...

Unused.

Value

A named list with elements `prob` (posterior probability that the summary of group `a` exceeds that of group `b`), `summary` (which summary was used), and `groups` (the two groups compared).