fix(#30488): make polycor an optional correlation dependency

Author: hidekoji

DESCRIPTION

@@ -14,7 +14,6 @@ Imports:
     prediction, 
     urltools,
     psych,
-    polycor,
     dplyr,
     tidyr,
     tibble,
@@ -46,6 +45,7 @@ Imports:
     pwr,
     readr
 Suggests:
+    polycor,
     testthat,
     twitteR,
     sentimentr,

R/stats_wrapper.R

@@ -317,7 +317,13 @@ do_cor_internal <- function(mat, use, method, diag, output_cols, na.rm) {
     # Polychoric coerces every column to ordered so every pair uses the ordinal model.
     # Mixed preserves continuous numerics and converts factor/logical columns to ordered,
     # allowing hetcor() to select Pearson, polyserial, or polychoric per pair.
-    loadNamespace("polycor")
+    if (!requireNamespace("polycor", quietly = TRUE)) {
+      stop(
+        "The 'polycor' package is required for polychoric and mixed correlations. ",
+        "Install it before using this method.",
+        call. = FALSE
+      )
+    }
     ordered_df <- as_hetcor_data_frame(mat, force_ordinal = identical(method, "polychoric"))
     # hetcor only supports "complete.obs" and "pairwise.complete.obs", while the other
     # methods (via cor()/cor.test()) also accept "everything", "all.obs", and

tests/testthat/test_stats_wrapper.R

@@ -151,6 +151,8 @@ test_that("do_cor automatic method selects the specified correlation family", {
 })
 
 test_that("do_cor supports automatic and mixed correlations with factor inputs", {
+  skip_if_not_installed("polycor")
+
   set.seed(456)
   n <- 100
   ordinal <- ordered(cut(rnorm(n), breaks = c(-Inf, -0.84, -0.25, 0.25, 0.84, Inf)))