From 5273772632d2fdd644580e0737857592b7436002 Mon Sep 17 00:00:00 2001
From: Temidayo Akindahunsi <98013820+TemidayoA@users.noreply.github.com>
Date: Sun, 16 Aug 2026 10:52:38 +0000
Subject: [PATCH] Fix R EBM outer bag score aggregation

Signed-off-by: Temidayo Akindahunsi <98013820+TemidayoA@users.noreply.github.com>
---
 R/R/ebm.R                       |  6 +++++-
 R/build.R                       |  9 +++++++++
 R/tests/outer_bag_aggregation.R | 29 +++++++++++++++++++++++++++++
 3 files changed, 43 insertions(+), 1 deletion(-)
 create mode 100644 R/tests/outer_bag_aggregation.R

diff --git a/R/R/ebm.R b/R/R/ebm.R
index 6090763f4..2e64d206b 100644
--- a/R/R/ebm.R
+++ b/R/R/ebm.R
@@ -112,7 +112,11 @@ ebm_classify <- function(
          rng
       )
       for(i_feature in 1:n_features) {
-         term_scores[[col_names[i_feature]]] <- result_list$model_update[[i_feature]]
+         if(1 == i_outer_bag) {
+            term_scores[[col_names[i_feature]]] <- result_list$model_update[[i_feature]]
+         } else {
+            term_scores[[col_names[i_feature]]] <- term_scores[[col_names[i_feature]]] + result_list$model_update[[i_feature]]
+         }
       }
    }
    for(col_name in col_names) {
diff --git a/R/build.R b/R/build.R
index de805ff56..5dcb5554f 100644
--- a/R/build.R
+++ b/R/build.R
@@ -56,6 +56,15 @@ for (file in list.files(file.path(root_path, "R"))) {
    file.copy(from = file.path(root_path, "R", file), to = file.path(dest_path, "R", file))
 }
 
+# tests directory
+tests_path <- file.path(root_path, "tests")
+if(dir.exists(tests_path)) {
+   dir.create(file.path(dest_path, "tests"))
+   for (file in list.files(tests_path)) {
+      file.copy(from = file.path(tests_path, file), to = file.path(dest_path, "tests", file))
+   }
+}
+
 # src directory (R C++ files)
 dir.create(file.path(dest_path, "src"))
 file.copy(from = file.path(root_path, "src", "interpret_R.cpp"), to = file.path(dest_path, "src", "interpret_R.cpp"))
diff --git a/R/tests/outer_bag_aggregation.R b/R/tests/outer_bag_aggregation.R
new file mode 100644
index 000000000..5d1c290eb
--- /dev/null
+++ b/R/tests/outer_bag_aggregation.R
@@ -0,0 +1,29 @@
+# Copyright (c) 2026 The InterpretML Contributors
+#
+# Licensed under the MIT license.
+
+library(interpret)
+
+X <- data.frame(x = seq_len(100))
+y <- c(rep(0, 90), rep(1, 10))
+
+model <- ebm_classify(
+   X,
+   y,
+   outer_bags = 16,
+   random_state = 42
+)
+
+probabilities <- ebm_predict_proba(model, X)
+difference <- abs(mean(probabilities) - mean(y))
+
+if(0.02 <= difference) {
+   stop(
+      sprintf(
+         "Expected mean probability near %.9f, got %.9f",
+         mean(y),
+         mean(probabilities)
+      ),
+      call. = FALSE
+   )
+}