explicit error for unsupported categorical features

R-package/R/xgb.Booster.R

@@ -1043,6 +1043,10 @@ xgb.best_iteration <- function(bst) {
   return(out)
 }
 
+xgb.has_categ_features <- function(bst) {
+  return("c" %in% xgb.feature_types(bst))
+}
+
 #' Extract coefficients from linear booster
 #'
 #' @description

R-package/R/xgb.model.dt.tree.R

@@ -2,8 +2,12 @@
 #'
 #' Parse a boosted tree model text dump into a `data.table` structure.
 #'
+#' Note that this function does not work with models that were fitted to
+#' categorical data.
 #' @param model Object of class `xgb.Booster`. If it contains feature names (they can
 #'   be set through [setinfo()]), they will be used in the output from this function.
+#'
+#'   If the model contains categorical features, an error will be thrown.
 #' @param text Character vector previously generated by the function [xgb.dump()]
 #'   (called with parameter `with_stats = TRUE`). `text` takes precedence over `model`.
 #' @param trees An integer vector of tree indices that should be used. The default
@@ -68,6 +72,10 @@ xgb.model.dt.tree <- function(model = NULL, text = NULL,
                               trees = NULL, use_int_id = FALSE, ...) {
   check.deprecation(...)
 
+  if (xgb.has_categ_features(model)) {
+    stop("Cannot produce tables for models having categorical features.")
+  }
+
   if (!inherits(model, "xgb.Booster") && !is.character(text)) {
     stop("Either 'model' must be an object of class xgb.Booster\n",
          "  or 'text' must be a character vector with the result of xgb.dump\n",

R-package/R/xgb.plot.multi.trees.R

@@ -2,6 +2,8 @@
 #'
 #' Visualization of the ensemble of trees as a single collective unit.
 #'
+#' Note that this function does not work with models that were fitted to
+#' categorical data.
 #' @details
 #' This function tries to capture the complexity of a gradient boosted tree model
 #' in a cohesive way by compressing an ensemble of trees into a single tree-graph representation.
@@ -66,6 +68,12 @@ xgb.plot.multi.trees <- function(model, features_keep = 5, plot_width = NULL, pl
     stop("DiagrammeR is required for xgb.plot.multi.trees")
   }
   check.deprecation(...)
+  if (xgb.has_categ_features(model)) {
+    stop(
+      "Cannot use 'xgb.plot.multi.trees' for models with categorical features.",
+      " Try 'xgb.plot.tree' instead."
+    )
+  }
   tree.matrix <- xgb.model.dt.tree(model = model)
 
   # first number of the path represents the tree, then the following numbers are related to the path to follow