possible issue with the posterior_vs_prior function when using regex_pars to match a single parameter occurrence #662

#
# R code apparently showing rstanarm::posterior_vs_prior() having a problem with
# regex_pars only matching one pars.
#

library(rstanarm)
#> Loading required package: Rcpp
#> This is rstanarm version 2.32.2
#> - See https://mc-stan.org/rstanarm/articles/priors for changes to default priors!
#> - Default priors may change, so it's safest to specify priors, even if equivalent to the defaults.
#> - For execution on a local, multicore CPU with excess RAM we recommend calling
#>   options(mc.cores = parallel::detectCores())
library(bayesplot)
#> This is bayesplot version 1.16.0
#> - Online documentation and vignettes at mc-stan.org/bayesplot
#> - bayesplot theme set to bayesplot::theme_default()
#>    * Does _not_ affect other ggplot2 plots
#>    * See ?bayesplot_theme_set for details on theme setting

# use the Pastes dataset
df1 <- lme4::Pastes

# ignore div_trans
fit_stan_lmer1 <- stan_lmer(strength ~ 1 + (1|batch/cask), data = df1)
#> 
#> SAMPLING FOR MODEL 'continuous' NOW (CHAIN 1).


fit_stan_lmer2 <- stan_lmer(strength ~ 1 + (1|batch), data = df1)
#> 
#> SAMPLING FOR MODEL 'continuous' NOW (CHAIN 1).


fit_stan_lmer3 <- stan_lmer(strength ~ 1 + (1|cask), data = df1)
#> 
#> SAMPLING FOR MODEL 'continuous' NOW (CHAIN 1).


# for conciseness
names_fit_stan_lmer1 <- names(as.data.frame(fit_stan_lmer1))
grep("b\\[", names_fit_stan_lmer1, value = TRUE, invert = TRUE)
#> [1] "(Intercept)"                              
#> [2] "sigma"                                    
#> [3] "Sigma[cask:batch:(Intercept),(Intercept)]"
#> [4] "Sigma[batch:(Intercept),(Intercept)]"

# posterior_vs_prior(fit_stan_lmer1, group_by_parameter = TRUE) + theme_default()  # ok
# posterior_vs_prior(fit_stan_lmer1, pars="alpha") + theme_default()  # ok
posterior_vs_prior(fit_stan_lmer1, pars="sigma")          # ok
#> 
#> Drawing from prior...
#> Warning: `aes_string()` was deprecated in ggplot2 3.0.0.
#> ℹ Please use tidy evaluation idioms with `aes()`.
#> ℹ See also `vignette("ggplot2-in-packages")` for more information.
#> ℹ The deprecated feature was likely used in the rstanarm package.
#>   Please report the issue at <https://github.com/stan-dev/rstanarm/issues>.
#> This warning is displayed once per session.
#> Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
#> generated.
#> Warning: The `size` argument of `grid_lines()` is deprecated as of bayesplot 1.16.0.
#> ℹ Please use the `linewidth` argument instead.
#> ℹ The deprecated feature was likely used in the rstanarm package.
#>   Please report the issue at <https://github.com/stan-dev/rstanarm/issues>.
#> This warning is displayed once per session.
#> Call `lifecycle::last_lifecycle_warnings()` to see where this warning was
#> generated.

#' ![](steep-carp_reprex_files/figure-gfm/unnamed-chunk-2-1.png)<!-- -->

posterior_vs_prior(fit_stan_lmer1, regex_pars = "sigma")  # Error dimensions
#> 
#> Drawing from prior...
#> Error in `s[, labs, drop = FALSE]`:
#> ! incorrect number of dimensions
posterior_vs_prior(fit_stan_lmer1, regex_pars = "sigm")   # Error dimensions
#> 
#> Drawing from prior...
#> Error in `s[, labs, drop = FALSE]`:
#> ! incorrect number of dimensions
posterior_vs_prior(fit_stan_lmer1, regex_pars = "igma")   # ok (matches 3)
#> 
#> Drawing from prior...

#' ![](steep-carp_reprex_files/figure-gfm/unnamed-chunk-2-2.png)<!-- -->

posterior_vs_prior(fit_stan_lmer1, regex_pars = "Sigma")  # ok (matches 2)
#> 
#> Drawing from prior...

#' ![](steep-carp_reprex_files/figure-gfm/unnamed-chunk-2-3.png)<!-- -->


# fit_stan_lmer2, fitting only batch without cask
names_fit_stan_lmer2 <- names(as.data.frame(fit_stan_lmer2))
grep("b\\[", names_fit_stan_lmer2, value = TRUE, invert = TRUE)
#> [1] "(Intercept)"                         
#> [2] "sigma"                               
#> [3] "Sigma[batch:(Intercept),(Intercept)]"

posterior_vs_prior(fit_stan_lmer2, regex_pars = "Sigma")  # Error dimensions
#> 
#> Drawing from prior...
#> Error in `s[, labs, drop = FALSE]`:
#> ! incorrect number of dimensions

# check fit_stan_lmer3, fitting only cask without batch
posterior_vs_prior(fit_stan_lmer3, regex_pars = "Sigma")  # Error dimensions
#> 
#> Drawing from prior...
#> Error in `s[, labs, drop = FALSE]`:
#> ! incorrect number of dimensions

# Is the reason (regex_pars = "Sigma") works for fit1 but not fit2 because fit2 has only 
# one match
#   "Sigma[batch:(Intercept),(Intercept)]"
# whereas fit1 had two matches?
#   "Sigma[cask:batch:(Intercept),(Intercept)]"
#   "Sigma[batch:(Intercept),(Intercept)]"
#
# same for fit3

#eof