R/posterior_t.R

In baymedr: Computation of Bayes Factors for Common Biomedical Designs

#' @import stats
posterior_t <- function(delta,
                        t,
                        n1,
                        n2 = NULL,
                        ind_samples = FALSE,
                        prior_loc,
                        prior_scale,
                        prior_df,
                        rel_tol = .Machine$double.eps^0.25) {
  neff <- ifelse(ind_samples,
                 n1 * n2 / (n1 + n2),
                 n1)
  nu <- ifelse(ind_samples,
               n1 + n2 - 2,
               n1 - 1)
  mu_delta <- prior_loc
  gamma <- prior_scale
  kappa <- prior_df
  numerator <- suppressWarnings(
    dt(
      x = t,
      df = nu,
      ncp = sqrt(neff) * delta) * 1 / gamma * dt(
        (delta - mu_delta) / gamma,
        df = kappa))
  denominator <- integrate(integrand_t,
                           lower = -Inf,
                           upper = Inf,
                           t = t,
                           n = neff,
                           nu = nu,
                           mu_delta = mu_delta,
                           gamma = gamma,
                           kappa = kappa,
                           rel.tol = rel_tol)$value
  out <- numerator / denominator
  out[is.na(out)] <- 0
  return(out)
}