Allow tidy_draws to work with rstanarm models with a single variable

R/tidy_draws.R

@@ -142,7 +142,7 @@ tidy_draws.data.frame = function(model, ...) {
 #' @export
 tidy_draws.mcmc.list = function(model, ...) {
   draws = do.call(rbind, lapply(seq_along(model), function(chain) {
-    n = nrow(model[[chain]])
+    n = coda::niter(model[[chain]])
     iteration = seq_len(n)
 
     add_column(
@@ -181,7 +181,14 @@ tidy_draws.stanreg = function(model, ...) {
   #so we dont' just do tidy_draws(model$stanfit)
   sample_matrix = as.array(model) #[iteration, chain, variable]
   n_chain = dim(sample_matrix)[[2]]
-  mcmc_list = as.mcmc.list(lapply(seq_len(n_chain), function(chain) as.mcmc(sample_matrix[, chain, ]))) # nolint
+  drop_second_dim <- function(x) {
+    x.dim <- dim(x)
+    x.dimnames <- dimnames(x)
+    dim(x) <- x.dim[-2]
+    dimnames(x) <- x.dimnames[-2]
+    x
+  }
+  mcmc_list = as.mcmc.list(lapply(seq_len(n_chain), function(chain) as.mcmc(drop_second_dim(sample_matrix[, chain, , drop=FALSE])))) # nolint
   draws = tidy_draws(mcmc_list, ...)
   draws = add_rstan_sampler_param_draws(draws, model$stanfit)
 

build_test_models.R

@@ -186,7 +186,7 @@ rstanarm.m_cyl = stan_glmer(mpg ~ (1|cyl), data = mtcars_tbl,
 )
 saveRDS(strip_rstanarm_model(rstanarm.m_cyl), "tests/models/models.rstanarm.m_cyl.rds", compress = "xz")
 
-#rstanarm model with random intercept
+# rstanarm model with random intercept
 set.seed(48431)
 rstanarm.m_ranef = stan_glmer(
   y ~ x + (1|group),
@@ -196,6 +196,16 @@ rstanarm.m_ranef = stan_glmer(
 )
 saveRDS(strip_rstanarm_model(rstanarm.m_ranef), "tests/models/models.rstanarm.m_ranef.rds", compress = "xz")
 
+# rstanarm model with one variable
+set.seed(48431)
+rstanarm.m_one_var <- stan_glm(cbind(hits, misses) ~ 1,
+                               data = data.frame(
+                                 hits = c(3L, 3L, 1L, 2L, 4L, 3L, 5L, 3L, 5L, 2L, 4L, 4L, 5L, 2L, 5L, 4L, 6L, 5L, 5L, 4L),
+                                 misses = c(15L, 10L, 15L, 8L, 7L, 13L, 15L, 8L, 15L, 10L, 6L, 10L, 9L, 17L, 10L, 15L, 10L, 13L, 9L, 10L)
+                               ), family = binomial(),
+                               warmup = 150, iter = 200, chains = 2, seed = 1, save_warmup = FALSE
+)
+saveRDS(strip_rstanarm_model(rstanarm.m_one_var), "tests/models/models.rstanarm.m_one_var.rds", compress = "xz")
 
 # Stan models -----------------------------------------------------------------
 set.seed(94302)

tests/testthat/test.tidy_draws.R

@@ -48,6 +48,13 @@ test_that("tidy_draws works with rstanarm", {
   expect_equal(tidy_draws(m_ranef), draws_tidy)
 })
 
+test_that("tidy_draws works with rstanarm models with one variable", {
+  skip_if_not_installed("rstanarm")
+
+  m_one_var = readRDS(test_path("../models/models.rstanarm.m_one_var.rds"))
+  expect_contains(colnames(tidy_draws(m_one_var)), "(Intercept)")
+})
+
 
 # rstan -------------------------------------------------------------------
 test_that("tidy_draws works with rstan", {