Posterior draws of the delay distribution parameters

Returns posterior draws of the parameters of the delay distribution in the long format used by tidybayes. The delay parameters are the distributional parameters of the brms family, evaluated on the response scale for each row of newdata. For a lognormal model they are mu and sigma. They are the parameters of the delay distribution itself, so they do not describe the censoring or truncation of the observation process, and they are not the natural scale mean and standard deviation of the delay. Use add_summaries() to add those.

add_delay_parameter_draws() is the same function with newdata first, for use at the start of a pipeline as with tidybayes::add_epred_draws().

Usage

delay_parameter_draws(object, newdata = NULL, ...)

add_delay_parameter_draws(newdata, object, ...)

Arguments

object

A model fit with epidist().

newdata

A data.frame of data to predict for. If NULL, the default, the data the model was fitted to is used. The brms models epidist fits need the model variables as well as the predictors, so build newdata with epidist_strata() rather than from the predictors alone.

...

Additional arguments passed to brms::prepare_predictions(), such as ndraws or re_formula.

Value

A tibble of posterior draws of the delay distribution parameters, grouped by the columns of newdata and by .row.

Details

The returned columns follow the tidybayes conventions. The columns of newdata come first, followed by .row, .chain, .iteration and .draw, followed by one column per distributional parameter. The result is grouped by the columns of newdata and by .row. .chain and .iteration are NA when the draws have been subset, because the chain a subset draw came from is not recoverable.

Every row of newdata gets its own draws, so passing the data the model was fitted to produces many identical draws when the model has few unique combinations of predictors. epidist_strata() returns one row per unique combination and is usually the better input.

See also

add_summaries() to add natural scale summaries of the delay, epidist_strata() to build newdata.

Other postprocess: add_summaries(), epidist_strata()

Examples

if (FALSE) { # \dontrun{
# `fit` is a model fitted with `epidist()`
fit |>
  epidist_strata() |>
  add_delay_parameter_draws(fit) |>
  add_summaries(probs = c(0.05, 0.95))
} # }