[MRG] Set min_impurity_split in gradient boosting models

Sebastian Pölsterl · Sebastian Pölsterl · commit c901cc561fd1 · 2016-12-13T18:34:12.000Z
self.min_impurity_split should be passed to DecisionTreeRegressor in BaseGradientBoosting._fit_stage. Fixes #8006
diff --git a/doc/whats_new.rst b/doc/whats_new.rst
@@ -127,6 +127,10 @@ API changes summary
      now only have ``self.estimators_`` available after ``fit``.
      :issue:`7464` by `Lars Buitinck`_ and `Loic Esteve`_.
 
+   - Fix a bug where :class:`sklearn.ensemble.GradientBoostingClassifier` and
+     :class:`sklearn.ensemble.GradientBoostingRegressor` ignored the
+     ``min_impurity_split`` parameter.
+     :issue:`8006` by :user:`Sebastian Pölsterl <sebp>`.
 
 .. _changes_0_18_1:
 
diff --git a/sklearn/ensemble/gradient_boosting.py b/sklearn/ensemble/gradient_boosting.py
@@ -765,6 +765,7 @@ def _fit_stage(self, i, X, y, y_pred, sample_weight, sample_mask,
                 min_samples_split=self.min_samples_split,
                 min_samples_leaf=self.min_samples_leaf,
                 min_weight_fraction_leaf=self.min_weight_fraction_leaf,
+                min_impurity_split=self.min_impurity_split,
                 max_features=self.max_features,
                 max_leaf_nodes=self.max_leaf_nodes,
                 random_state=random_state,
diff --git a/sklearn/ensemble/tests/test_gradient_boosting.py b/sklearn/ensemble/tests/test_gradient_boosting.py
@@ -961,6 +961,19 @@ def test_max_leaf_nodes_max_depth():
         assert_equal(tree.max_depth, 1)
 
 
+def test_min_impurity_split():
+    # Test if min_impurity_split of base estimators is set
+    # Regression test for #8006
+    X, y = datasets.make_hastie_10_2(n_samples=100, random_state=1)
+    all_estimators = [GradientBoostingRegressor,
+                      GradientBoostingClassifier]
+
+    for GBEstimator in all_estimators:
+        est = GBEstimator(min_impurity_split=0.1).fit(X, y)
+        for tree in est.estimators_.flat:
+            assert_equal(tree.min_impurity_split, 0.1)
+
+
 def test_warm_start_wo_nestimators_change():
     # Test if warm_start does nothing if n_estimators is not changed.
     # Regression test for #3513.
