diff --git a/vignettes/faq.Rmd b/vignettes/faq.Rmd index ad9285d7f..e8b278370 100644 --- a/vignettes/faq.Rmd +++ b/vignettes/faq.Rmd @@ -88,11 +88,22 @@ For an example use of these functions, have a look at the [`epidist-paper`](http However, some of those priors do not make sense in the context of our application. Instead, we used [prior predictive checking](https://mc-stan.org/docs/stan-users-guide/posterior-predictive-checks.html) to set `epidist`-specific default priors which produce epidemiological delay distribution mean and standard deviation parameters in a reasonable range. -For example, here are summary statistics for the distributions on the delay distribution mean and standard deviation, as implied by the following prior distributions on the `brms` lognormal `mu` and `sigma` parameters -$$ -\mu \sim \mathcal{N}(2, 0.5^2), \\ -\sigma \sim \mathcal{N}(0, 0.5^2). -$$ +For example, for the lognormal latent individual model, we suggest the following prior distributions for the `brms` `mu` and `sigma` parameters: + +```{r} +epidist_family <- epidist_family(data = data, family = brms::lognormal) +epidist_prior <- epidist_prior( + data = data, + family = epidist_family, + formula = brms::bf(mu ~ 1, sigma ~ 1) +) + +epidist_prior +``` + +(Note that the functions `epidist_family` and `epidist_prior` are mostly for internal use!) + +Here are summary statistics for the distributions on the delay distribution mean and standard deviation parameters that these prior distributions imply: ```{r message=FALSE, results='hide'} set.seed(1) @@ -107,6 +118,6 @@ summary(pred$mean) summary(pred$sd) ``` -Note that even with these quite restricted prior distributions, there are still some very large samples of the delay mean and standard deviation (which arguably are not plausible a-priori)! +(Note that even with these quite restricted prior distributions, there are still some very large samples of the delay mean and standard deviation [which arguably are not plausible a-priori]!) ## Bibliography