Fixed .var for arrays with 1 more valid value than ddofs

2 files changed, 15 insertions, 2 deletions

diff --git a/numpy/ma/core.py b/numpy/ma/core.py
index ff9fc4f4e..61c3a9761 100644
--- a/numpy/ma/core.py
+++ b/numpy/ma/core.py
@@ -4743,7 +4743,7 @@ class MaskedArray(ndarray):
         dvar = divide(danom.sum(axis), cnt).view(type(self))
         # Apply the mask if it's not a scalar
         if dvar.ndim:
-            dvar._mask = mask_or(self._mask.all(axis), (cnt <= ddof))
+            dvar._mask = mask_or(self._mask.all(axis), (cnt <= 0))
             dvar._update_from(self)
         elif getattr(dvar, '_mask', False):
         # Make sure that masked is returned when the scalar is masked.
diff --git a/numpy/ma/tests/test_core.py b/numpy/ma/tests/test_core.py
index 014af2d73..f95d621db 100644
--- a/numpy/ma/tests/test_core.py
+++ b/numpy/ma/tests/test_core.py
@@ -199,7 +199,7 @@ class TestMaskedArray(TestCase):
         err_status_ini = np.geterr()
         try:
             np.seterr(invalid='ignore')
-            data = masked_array(np.sqrt([-1., 0., 1.]), mask=[0, 0, 1])
+            data = masked_array([np.nan, 0., 1.], mask=[0, 0, 1])
             data_fixed = fix_invalid(data)
             assert_equal(data_fixed._data, [data.fill_value, 0., 1.])
             assert_equal(data_fixed._mask, [1., 0., 1.])
@@ -2707,6 +2707,19 @@ class TestMaskedArrayMathMethods(TestCase):
             self.assertTrue(np.isnan(nout))
 
 
+    def test_varstd_ddof(self):
+        a = array([[1, 1, 0], [1, 1, 0]], mask=[[0, 0, 1], [0, 0, 1]])
+        test = a.std(axis=0, ddof=0)
+        assert_equal(test.filled(0), [0, 0, 0])
+        assert_equal(test.mask, [0, 0, 1])
+        test = a.std(axis=0, ddof=1)
+        assert_equal(test.filled(0), [0, 0, 0])
+        assert_equal(test.mask, [0, 0, 1])
+        test = a.std(axis=0, ddof=2)
+        assert_equal(test.filled(0), [0, 0, 0])
+        assert_equal(test.mask, [1, 1, 1])
+
+
     def test_diag(self):
         "Test diag"
         x = arange(9).reshape((3, 3))