finalized kurt and skew fix pd.series

Author: Sebastian Goldmann

pandas/core/nanops.py

@@ -1287,10 +1287,10 @@ def nanskew(
         result = result.astype(dtype, copy=False)
 
     if isinstance(result, np.ndarray):
-        result = np.where(m2 == 0, 0, result)
+        result = np.where(m2 == 0, np.nan, result)
         result[count < 3] = np.nan
     else:
-        result = dtype.type(0) if m2 == 0 else result
+        result = np.nan if m2 == 0 else result
         if count < 3:
             return np.nan
 

pandas/tests/test_nanops.py

@@ -559,10 +559,10 @@ def _skew_kurt_wrap(self, values, axis=None, func=None):
         result = func(values, axis=axis, bias=False)
         # fix for handling cases where all elements in an axis are the same
         if isinstance(result, np.ndarray):
-            result[np.max(values, axis=axis) == np.min(values, axis=axis)] = 0
+            result[np.max(values, axis=axis) == np.min(values, axis=axis)] = np.nan
             return result
         elif np.max(values) == np.min(values):
-            return 0.0
+            return np.nan
         return result
 
     def test_nanskew(self, skipna):
@@ -1021,7 +1021,7 @@ def test_constant_series(self, val):
         # xref GH 11974
         data = val * np.ones(300)
         skew = nanops.nanskew(data)
-        assert skew == 0.0
+        assert np.isnan(skew)
 
     def test_all_finite(self):
         alpha, beta = 0.3, 0.1
@@ -1089,7 +1089,7 @@ def test_constant_series(self, val):
         # xref GH 11974
         data = val * np.ones(300)
         kurt = nanops.nankurt(data)
-        tm.assert_equal(kurt, 0.0)
+        tm.assert_equal(kurt, np.nan)
 
     def test_all_finite(self):
         alpha, beta = 0.3, 0.1