Fix missing drop = FALSE in nuts_params.CmdStanMCMC()

NEWS.md

@@ -1,5 +1,6 @@
 # bayesplot (development version)
 
+* Fixed missing `drop = FALSE` in `nuts_params.CmdStanMCMC()`.
 * Replace `apply()` with `storage.mode()` for integer-to-numeric matrix conversion in `validate_predictions()`.
 * Fixed `is_chain_list()` to correctly reject empty lists instead of silently returning `TRUE`.
 * Added unit tests for `mcmc_areas_ridges_data()`, `mcmc_parcoord_data()`, and `mcmc_trace_data()`.

R/bayesplot-extractors.R

@@ -175,7 +175,7 @@ nuts_params.list <- function(object, pars = NULL, ...) {
 nuts_params.CmdStanMCMC <- function(object, pars = NULL, ...) {
   arr <- object$sampler_diagnostics()
   if (!is.null(pars)) {
-    arr <- arr[,, pars]
+    arr <- arr[,, pars, drop = FALSE]
   }
   out <- reshape2::melt(arr)
   colnames(out)[colnames(out) == "variable"] <- "parameter"

tests/testthat/test-extractors.R

@@ -136,4 +136,12 @@ test_that("cmdstanr methods work", {
   ratio <- neff_ratio(fit)
   expect_named(head(ratio, 4), c("alpha", "beta[1]", "beta[2]", "beta[3]"))
   expect_true(all(ratio > 0))
+
+  # https://github.com/stan-dev/bayesplot/pull/535
+  np_one <- nuts_params(fit, pars = "divergent__")
+  expect_identical(levels(np_one$Parameter), "divergent__")
+  expect_true(all(np_one$Parameter == "divergent__"))
+  expect_equal(range(np_one$Iteration), c(1, 500))
+  expect_equal(range(np_one$Chain), c(1, 2))
+  expect_true(all(np_one$Value == 0))
 })