Running examples in ‘projpred-Ex.R’ failed
The error most likely occurred in:

> ### Name: as.matrix.projection
> ### Title: Extract projected parameter draws
> ### Aliases: as.matrix.projection
> 
> ### ** Examples
> 
> if (requireNamespace("rstanarm", quietly = TRUE)) {
+   # Data:
+   dat_gauss <- data.frame(y = df_gaussian$y, df_gaussian$x)
+ 
+   # The "stanreg" fit which will be used as the reference model (with small
+   # values for `chains` and `iter`, but only for technical reasons in this
+   # example; this is not recommended in general):
+   fit <- rstanarm::stan_glm(
+     y ~ X1 + X2 + X3 + X4 + X5, family = gaussian(), data = dat_gauss,
+     QR = TRUE, chains = 2, iter = 500, refresh = 0, seed = 9876
+   )
+ 
+   # Projection onto an arbitrary combination of predictor terms (with a small
+   # value for `nclusters`, but only for the sake of speed in this example;
+   # this is not recommended in general):
+   prj <- project(fit, solution_terms = c("X1", "X3", "X5"), nclusters = 10,
+                  seed = 9182)
+   prjmat <- as.matrix(prj)
+   ### For further post-processing (e.g., via packages `bayesplot` and
+   ### `posterior`), we will here ignore the fact that clustering was used
+   ### (due to argument `nclusters` above). CAUTION: Ignoring the clustering
+   ### is not recommended and only shown here for demonstrative purposes. A
+   ### better solution for the clustering case is explained below.
+   # If the `bayesplot` package is installed, the output from
+   # as.matrix.projection() can be used there. For example:
+   if (requireNamespace("bayesplot", quietly = TRUE)) {
+     print(bayesplot::mcmc_intervals(prjmat))
+   }
+   # If the `posterior` package is installed, the output from
+   # as.matrix.projection() can be used there. For example:
+   if (requireNamespace("posterior", quietly = TRUE)) {
+     prjdrws <- posterior::as_draws_matrix(prjmat)
+     print(posterior::summarize_draws(
+       prjdrws,
+       "median", "mad", function(x) quantile(x, probs = c(0.025, 0.975))
+     ))
+   }
+   ### Better solution for post-processing clustered draws (e.g., via
+   ### `bayesplot` or `posterior`): Don't ignore the fact that clustering was
+   ### used. Instead, resample the clusters according to their weights (e.g.,
+   ### via posterior::resample_draws()). However, this requires access to the
+   ### cluster weights which is not implemented in `projpred` yet. This
+   ### example will be extended as soon as those weights are accessible.
+ }
Error in qr.default(xtemp) : object '.F_dqrdc2' not found
Calls: <Anonymous> -> stan_glm.fit -> qr -> qr.default
Execution halted