center is not implemented for offset based windows

Author: jreback

pandas/core/window.py

@@ -1028,6 +1028,12 @@ def validate(self):
                                  "compat with a datetimelike "
                                  "index".format(self.window))
 
+            # we don't allow center
+            if self.center:
+                raise NotImplementedError("center is not implemented "
+                                          "for datetimelike and offset "
+                                          "based windows")
+
             # this will raise ValueError on non-fixed freqs
             self.window = freq.nanos
             self.win_type = 'freq'

pandas/tests/test_window.py

@@ -3129,6 +3129,10 @@ def test_valid(self):
             with self.assertRaises(ValueError):
                 df.rolling(window='1D', min_periods=minp)
 
+        # center is not implemented
+        with self.assertRaises(NotImplementedError):
+            df.rolling(window='1D', center=True)
+
     def test_on(self):
 
         df = self.regular