fix case with matrix=FALSE and 1 parameter

Author: venpopov

R/args.R

@@ -254,6 +254,9 @@ SampleArgs <- R6::R6Class(
             fileext = ".json"
           )
         for (i in seq_along(inv_metric_paths)) {
+          if (length(inv_metric[[i]] == 1) && metric == "diag_e") {
+            inv_metric[[i]] <- array(inv_metric[[i]], dim = c(1))
+          }
           write_stan_json(list(inv_metric = inv_metric[[i]]), inv_metric_paths[i])
         }
 

R/fit.R

@@ -1743,6 +1743,9 @@ inv_metric <- function(matrix = TRUE) {
   if (matrix && !is.matrix(out[[1]])) {
     # convert each vector to a diagonal matrix
     out <- lapply(out, diag)
+  } else if (length(out[[1]]) == 1) {
+    # convert each scalar to a 1x1 matrix
+    out <- lapply(out, array, dim = c(1))
   }
   out
 }