Exponential prior on a positive scalar. Currently supported for
prior_sigma (normal-family residual SD) only; rejected for
unconstrained intercepts and regression coefficients.
prior_exponential(rate = 1) has mean 1 and is a reasonable
weakly-informative choice when the outcome is standardized.
Usage
prior_exponential(rate = 1)
Arguments
- rate
Rate parameter (default 1). Larger rate = tighter prior
concentrated near zero.
Value
A list with components distribution = "exponential", rate,
and placeholders (mean = 0, sd = 1 / rate) so the same
Stan-field translation works.
Examples
prior_exponential(rate = 1)
#> $distribution
#> [1] "exponential"
#>
#> $rate
#> [1] 1
#>
#> $mean
#> [1] 0
#>
#> $sd
#> [1] 1
#>
#> $df
#> [1] NA
#>
#> $autoscale
#> [1] FALSE
#>
