Add CFTimeIndex.shift

doc/api-hidden.rst

@@ -151,3 +151,5 @@
    plot.FacetGrid.set_titles
    plot.FacetGrid.set_ticks
    plot.FacetGrid.map
+
+   CFTimeIndex.shift

doc/whats-new.rst

@@ -49,12 +49,25 @@ Enhancements
 - Added :py:meth:`~xarray.CFTimeIndex.shift` for shifting the values of a
   CFTimeIndex by a specified frequency.  (:issue:`2244`).  By `Spencer Clark
   <https://github.com/spencerkclark>`_.
+- Added support for using ``cftime.datetime`` coordinates with
+  :py:meth:`~xarray.DataArray.differentiate`,
+  :py:meth:`~xarray.Dataset.differentiate`,
+  :py:meth:`~xarray.DataArray.interp`, and
+  :py:meth:`~xarray.Dataset.interp`.
+  By `Spencer Clark <https://github.com/spencerkclark>`_
 
 Bug fixes
 ~~~~~~~~~
 
 - Addition and subtraction operators used with a CFTimeIndex now preserve the
   index's type. (:issue:`2244`). By `Spencer Clark <https://github.com/spencerkclark>`_.
+- ``xarray.DataArray.roll`` correctly handles multidimensional arrays.
+  (:issue:`2445`)
+  By `Keisuke Fujii <https://github.com/fujiisoup>`_.
+
+- ``xarray.DataArray.std()`` now correctly accepts ``ddof`` keyword argument.
+  (:issue:`2240`)
+  By `Keisuke Fujii <https://github.com/fujiisoup>`_.
 
 .. _whats-new.0.10.9:
 

xarray/coding/cftimeindex.py

@@ -318,7 +318,7 @@ def contains(self, key):
     def shift(self, n, freq):
         """Shift the CFTimeIndex a multiple of the given frequency.
 
-        See the documentation for :py:func:`~xarray.cftime_range()` for a
+        See the documentation for :py:func:`~xarray.cftime_range` for a
         complete listing of valid frequency strings.
 
         Parameters
@@ -338,7 +338,6 @@ def shift(self, n, freq):
 
         Examples
         --------
-
         >>> index = xr.cftime_range('2000', periods=1, freq='M')
         >>> index
         CFTimeIndex([2000-01-31 00:00:00], dtype='object')
@@ -366,3 +365,32 @@ def __radd__(self, other):
 
     def __sub__(self, other):
         return CFTimeIndex(np.array(self) - other)
+
+
+def _parse_iso8601_without_reso(date_type, datetime_str):
+    date, _ = _parse_iso8601_with_reso(date_type, datetime_str)
+    return date
+
+
+def _parse_array_of_cftime_strings(strings, date_type):
+    """Create a numpy array from an array of strings.
+
+    For use in generating dates from strings for use with interp.  Assumes the
+    array is either 0-dimensional or 1-dimensional.
+
+    Parameters
+    ----------
+    strings : array of strings
+        Strings to convert to dates
+    date_type : cftime.datetime type
+        Calendar type to use for dates
+
+    Returns
+    -------
+    np.array
+    """
+    if strings.ndim == 0:
+        return np.array(_parse_iso8601_without_reso(date_type, strings.item()))
+    else:
+        return np.array([_parse_iso8601_without_reso(date_type, s)
+                         for s in strings])

xarray/tests/test_cftimeindex.py

@@ -683,3 +683,21 @@ def test_cftimeindex_shift_invalid_freq():
     index = xr.cftime_range('2000', periods=3)
     with pytest.raises(TypeError):
         index.shift(1, 1)
+
+
+@requires_cftime
+def test_parse_array_of_cftime_strings():
+    from cftime import DatetimeNoLeap
+
+    strings = np.array(['2000-01-01', '2000-01-02'])
+    expected = np.array([DatetimeNoLeap(2000, 1, 1),
+                         DatetimeNoLeap(2000, 1, 2)])
+
+    result = _parse_array_of_cftime_strings(strings, DatetimeNoLeap)
+    np.testing.assert_array_equal(result, expected)
+
+    # Test scalar array case
+    strings = np.array('2000-01-01')
+    expected = np.array(DatetimeNoLeap(2000, 1, 1))
+    result = _parse_array_of_cftime_strings(strings, DatetimeNoLeap)
+    np.testing.assert_array_equal(result, expected)