Merge pull request #21993 from rcomer/ma-minimum-fix

mattip · web-flow · commit a87031f25e4f · 2022-07-17T09:24:31.000+03:00
BUG: fix ma.minimum.reduce with axis keyword
diff --git a/numpy/ma/core.py b/numpy/ma/core.py
@@ -6875,6 +6875,8 @@ def reduce(self, target, axis=np._NoValue, **kwargs):
 
         if m is nomask:
             t = self.f.reduce(target.view(np.ndarray), **kwargs)
+            if isinstance(t, ndarray):
+                t = MaskedArray(t, mask=nomask)
         else:
             target = target.filled(
                 self.fill_value_func(target)).view(type(target))
diff --git a/numpy/ma/tests/test_core.py b/numpy/ma/tests/test_core.py
@@ -1235,6 +1235,18 @@ def test_minmax_reduce(self):
         b = np.maximum.reduce(a)
         assert_equal(b, 3)
 
+    def test_minmax_reduce_axis(self):
+        # Test np.min/maximum.reduce along an axis for 2D array
+        import numpy as np
+        data = [[0, 1, 2, 3, 4, 9], [5, 5, 0, 9, 3, 3]]
+        mask = [[0, 0, 0, 0, 0, 1], [0, 0, 1, 1, 0, 0]]
+        a = array(data, mask=mask)
+
+        expected = array([0, 3], mask=False)
+        result = np.minimum.reduce(a, axis=1)
+
+        assert_array_equal(result, expected)
+
     def test_minmax_funcs_with_output(self):
         # Tests the min/max functions with explicit outputs
         mask = np.random.rand(12).round()
