The object in slot fit is an object of type
stanfit from the rstan package. The pi_star variable contains
MCMC samples of the probability of at least one event in a single unit of
time, suitable to form the prior for a new trial that is exchangeable with
the historical trials. The ess variable contains samples for the
effective sample size of the distribution of pi_star. avg contains
samples for the mean of pi_star. The pi_h[i] variables contains
samples for the probability of at least one event in a single unit of time
for historical trials 1, 2...
See also
stan_map_summary_data() and stan_map_patient_data()
for examples.