Handle level

Author: TomAugspurger

pandas/core/generic.py

@@ -7692,7 +7692,7 @@ def stat_func(self, axis=None, skipna=None, level=None, numeric_only=None,
             axis = self._stat_axis_number
         if level is not None:
             return self._agg_by_level(name, axis=axis, level=level,
-                                      skipna=skipna)
+                                      skipna=skipna, min_count=min_count)
         return self._reduce(f, name, axis=axis, skipna=skipna,
                             numeric_only=numeric_only, min_count=min_count)
 

pandas/tests/series/test_analytics.py

@@ -124,6 +124,28 @@ def test_empty(self, method, unit, use_bottleneck):
             result = getattr(s, method)(min_count=2)
             assert isna(result)
 
+    @pytest.mark.parametrize('method, unit', [
+        ('sum', 0.0),
+        ('prod', 1.0),
+    ])
+    def test_empty_multi(self, method, unit):
+        s = pd.Series([1, np.nan, np.nan, np.nan],
+                      index=pd.MultiIndex.from_product([('a', 'b'), (0, 1)]))
+        # NaN by default
+        result = getattr(s, method)(level=0)
+        expected = pd.Series([1, np.nan], index=['a', 'b'])
+        tm.assert_series_equal(result, expected)
+
+        # min_count=0
+        result = getattr(s, method)(level=0, min_count=0)
+        expected = pd.Series([1, unit], index=['a', 'b'])
+        tm.assert_series_equal(result, expected)
+
+        # min_count=1
+        result = getattr(s, method)(level=0, min_count=1)
+        expected = pd.Series([1, np.nan], index=['a', 'b'])
+        tm.assert_series_equal(result, expected)
+
     @pytest.mark.parametrize(
         "method", ['sum', 'mean', 'median', 'std', 'var'])
     def test_ops_consistency_on_empty(self, method):