Create a Backend-Independent Prior Specification

Creates an inspectable prior table for one approved model family. The returned object contains no backend-specific prior objects and performs no sampling.

Usage

create_prior_specification(
  contract,
  baseline = NULL,
  intercept_scale = NULL,
  coefficient_scale = NULL,
  group_sd_scale = 1,
  residual_scale = NULL,
  correlation_eta = 2,
  student_df = 3
)

Arguments

contract

A gp3bayes_model_contract created by create_model_contract().

baseline

Numeric scalar describing the expected baseline outcome. For binary models this is a probability strictly between zero and one. The default is 0.5. For duration models this is a strictly positive baseline median in the recorded outcome unit and must be supplied.

intercept_scale

Optional positive numeric scalar for the normal intercept prior. Defaults to 1.5 for binary models and 1 for duration models.

coefficient_scale

Optional positive numeric scalar for normal population-level coefficient priors. Defaults to 1 for binary models and 0.5 for duration models.

group_sd_scale

Positive numeric scalar for half-Student-t group-level standard-deviation priors.

residual_scale

Optional positive numeric scalar for the half-Student-t residual standard-deviation prior. It applies only to the duration family and defaults to 1.

correlation_eta

Numeric scalar greater than or equal to one for the LKJ prior used when a participant-level random slope is requested.

student_df

Positive numeric scalar giving the degrees of freedom for half-Student-t scale priors.

Value

An object of class gp3bayes_prior_specification.

Details

Binary baseline probabilities are transformed with the logit function. Duration baseline medians are transformed with the natural logarithm.

Examples

binary_contract <- create_model_contract(
  family = "binary",
  outcome_col = "selected",
  participant_col = "participant_id"
)

create_prior_specification(
  binary_contract,
  baseline = 0.35
)
#> <gp3bayes_prior_specification>
#>   Family: binary
#>   Baseline: 0.35
#>   Parameter classes: Intercept, b, sd
#>   Backend: none
#>   Executable: FALSE