Posterior Predictive Draws

Draw replicated numerator and denominator responses from the posterior predictive distribution: at each posterior draw the two fitted means are assembled from that draw's parameters, and a response is drawn from the family at those means. The replicates are what pp_check() compares the observed data against.

Usage

# S3 method for class 'ratiod_fit'
posterior_predict(object, ndraws = NULL, ...)

Arguments

object

A ratiod_fit object

ndraws

Number of posterior draws to replicate. NULL (the default) uses every draw; a smaller number takes a random subsample.

...

Unused.

Value

A list with y_num_rep and y_denom_rep, each a draws-by-observation matrix, plus y_num and y_denom, the observed responses. A family with a fixed denominator (the binomial arms, whose denominator is the trial count) reports the trials as y_denom_rep.

See also

pp_check()

Examples

# \donttest{
set.seed(4)
n <- 40
df <- data.frame(
  count = rpois(n, 12),
  total = rpois(n, 80),
  x = rnorm(n)
)
fit <- tratio(count | total ~ x, data = df,
              family = ratiod_poisson_gamma(),
              control = list(iter = 400, chains = 1, seed = 1))
rep <- posterior_predict(fit, ndraws = 50)
dim(rep$y_num_rep)
#> [1] 50 40
# }