BUG: Fix masked median multiple masked arrays (numpy#21999)

bsipocz · jsclose · web-flow · commit 6b8d55e66e53 · 2022-07-17T15:58:53.000+03:00
Fixed issue that occurs when trying to take the median of a list of masked arrays. Added a check to see if the input is a list then converts to a masked array. See issue numpy#10757 for more information. Co-authored-by: jsclose <jsclose@umich.edu>
diff --git a/numpy/ma/extras.py b/numpy/ma/extras.py
@@ -723,7 +723,10 @@ def median(a, axis=None, out=None, overwrite_input=False, keepdims=False):
            fill_value=1e+20)
 
     """
-    if not hasattr(a, 'mask'):
+
+    a = np.ma.asarray(a)
+
+    if a.mask is np.ma.nomask:
         m = np.median(getdata(a, subok=True), axis=axis,
                       out=out, overwrite_input=overwrite_input,
                       keepdims=keepdims)
diff --git a/numpy/ma/tests/test_extras.py b/numpy/ma/tests/test_extras.py
@@ -1160,6 +1160,25 @@ def test_object(self):
         o[2] = np.nan
         assert_(type(np.ma.median(o.astype(object))), float)
 
+    def test_list_of_masked_array(self):
+        data1 = np.array([[1, 2, 3, 4], [5, 6, 7, 8]])
+        masked1 = np.ma.masked_where(data1 == 4, data1)
+        data2 = np.array([[8, 7, 6, 5], [4, 3, 2, 1]])
+        masked2 = np.ma.masked_where(data2 == 4, data2)
+        list = [masked1, masked2]
+        median_masked_list = np.ma.median(list, axis=0).data
+        assert_equal(median_masked_list,
+                     np.array([[4.5, 4.5, 4.5, 5], [5, 4.5, 4.5, 4.5]]))
+
+    def test_list_of_masked_array_no_axis(self):
+        data1 = np.array([[1, 2, 3, 4], [5, 6, 7, 8]])
+        masked1 = np.ma.masked_where(data1 == 2, data1)
+        data2 = np.array([[8, 7, 6, 5], [4, 3, 2, 1]])
+        masked2 = np.ma.masked_where(data2 == 5, data2)
+        list = [masked1, masked2]
+        median_masked_list = np.ma.median(list)
+        assert_equal(median_masked_list, 4.5)
+
 
 class TestCov:
 
