Honor keep_attrs in DataArray.quantile (#3305)

* Added `keep_attrs` argument to Variable.quantile. TestDataArray.test_quantile now checks for attributes in output.

* black

* updated whats new.

* removed vestigial comment. Switched default Variable.quantile keep_attrs to False.

doc/whats-new.rst

@@ -26,8 +26,8 @@ Breaking changes
 
 - The ``isel_points`` and ``sel_points`` methods are removed, having been deprecated
   since v0.10.0. These are redundant with the ``isel`` / ``sel`` methods.
-  See :ref:`vectorized_indexing` for the details 
-  By `Maximilian Roos <https://github.com/max-sixty>`_ 
+  See :ref:`vectorized_indexing` for the details
+  By `Maximilian Roos <https://github.com/max-sixty>`_
 - The ``inplace`` kwarg for public methods now raises an error, having been deprecated
   since v0.11.0.
   By `Maximilian Roos <https://github.com/max-sixty>`_
@@ -52,12 +52,12 @@ Breaking changes
     error in a later release.
 
   (:issue:`3250`) by `Guido Imperiale <https://github.com/crusaderky>`_.
-- :py:meth:`~Dataset.to_dataset` requires ``name`` to be passed as a kwarg (previously ambiguous 
+- :py:meth:`~Dataset.to_dataset` requires ``name`` to be passed as a kwarg (previously ambiguous
   positional arguments were deprecated)
 - Reindexing with variables of a different dimension now raise an error (previously deprecated)
-- :py:func:`~xarray.broadcast_array` is removed (previously deprecated in favor of 
+- :py:func:`~xarray.broadcast_array` is removed (previously deprecated in favor of
   :py:func:`~xarray.broadcast`)
-- :py:meth:`~Variable.expand_dims` is removed (previously deprecated in favor of 
+- :py:meth:`~Variable.expand_dims` is removed (previously deprecated in favor of
   :py:meth:`~Variable.set_dims`)
 
 New functions/methods
@@ -90,7 +90,7 @@ New functions/methods
   and `Maximilian Roos <https://github.com/max-sixty>`_.
 
 - Added :py:meth:`DataArray.broadcast_like` and :py:meth:`Dataset.broadcast_like`.
-  By `Deepak Cherian <https://github.com/dcherian>`_ and `David Mertz 
+  By `Deepak Cherian <https://github.com/dcherian>`_ and `David Mertz
   <http://github.com/DavidMertz>`_.
 
 - Dataset plotting API for visualizing dependencies between two `DataArray`s!
@@ -131,14 +131,14 @@ Enhancements
   :py:meth:`DataArray.set_index`, as well are more specific error messages
   when the user passes invalid arguments (:issue:`3176`).
   By `Gregory Gundersen <https://github.com/gwgundersen>`_.
-  
+
 - :py:func:`filter_by_attrs` now filters the coordinates as well as the variables. By `Spencer Jones <https://github.com/cspencerjones>`_.
 
 Bug fixes
 ~~~~~~~~~
 
-- Improve "missing dimensions" error message for :py:func:`~xarray.apply_ufunc` 
-  (:issue:`2078`). 
+- Improve "missing dimensions" error message for :py:func:`~xarray.apply_ufunc`
+  (:issue:`2078`).
   By `Rick Russotto <https://github.com/rdrussotto>`_.
 - :py:meth:`~xarray.DataArray.assign_coords` now supports dictionary arguments
   (:issue:`3231`).
@@ -170,6 +170,8 @@ Bug fixes
   dask compute (:issue:`3237`). By `Ulrich Herter <https://github.com/ulijh>`_.
 - Plots in 2 dimensions (pcolormesh, contour) now allow to specify levels as numpy
   array (:issue:`3284`). By `Mathias Hauser <https://github.com/mathause>`_.
+- Fixed bug in :meth:`DataArray.quantile` failing to keep attributes when
+  `keep_attrs` was True (:issue:`3304`). By David Huard <https://github.com/huard>`_.
 
 .. _whats-new.0.12.3:
 

xarray/core/dataset.py

@@ -4831,7 +4831,10 @@ def quantile(
                             # the former is often more efficient
                             reduce_dims = None
                         variables[name] = var.quantile(
-                            q, dim=reduce_dims, interpolation=interpolation
+                            q,
+                            dim=reduce_dims,
+                            interpolation=interpolation,
+                            keep_attrs=keep_attrs,
                         )
 
             else:

xarray/core/variable.py

@@ -1592,7 +1592,7 @@ def no_conflicts(self, other):
         """
         return self.broadcast_equals(other, equiv=duck_array_ops.array_notnull_equiv)
 
-    def quantile(self, q, dim=None, interpolation="linear"):
+    def quantile(self, q, dim=None, interpolation="linear", keep_attrs=None):
         """Compute the qth quantile of the data along the specified dimension.
 
         Returns the qth quantiles(s) of the array elements.
@@ -1615,6 +1615,10 @@ def quantile(self, q, dim=None, interpolation="linear"):
                 * higher: ``j``.
                 * nearest: ``i`` or ``j``, whichever is nearest.
                 * midpoint: ``(i + j) / 2``.
+        keep_attrs : bool, optional
+            If True, the variable's attributes (`attrs`) will be copied from
+            the original object to the new one.  If False (default), the new
+            object will be returned without attributes.
 
         Returns
         -------
@@ -1623,7 +1627,7 @@ def quantile(self, q, dim=None, interpolation="linear"):
             is a scalar. If multiple percentiles are given, first axis of
             the result corresponds to the quantile and a quantile dimension
             is added to the return array. The other dimensions are the
-             dimensions that remain after the reduction of the array.
+            dimensions that remain after the reduction of the array.
 
         See Also
         --------
@@ -1651,14 +1655,19 @@ def quantile(self, q, dim=None, interpolation="linear"):
             axis = None
             new_dims = []
 
-        # only add the quantile dimension if q is array like
+        # Only add the quantile dimension if q is array-like
         if q.ndim != 0:
             new_dims = ["quantile"] + new_dims
 
         qs = np.nanpercentile(
             self.data, q * 100.0, axis=axis, interpolation=interpolation
         )
-        return Variable(new_dims, qs)
+
+        if keep_attrs is None:
+            keep_attrs = _get_keep_attrs(default=False)
+        attrs = self._attrs if keep_attrs else None
+
+        return Variable(new_dims, qs, attrs)
 
     def rank(self, dim, pct=False):
         """Ranks the data.

xarray/tests/test_dataarray.py

@@ -2333,17 +2333,17 @@ def test_reduce_out(self):
         with pytest.raises(TypeError):
             orig.mean(out=np.ones(orig.shape))
 
-    # skip due to bug in older versions of numpy.nanpercentile
     def test_quantile(self):
         for q in [0.25, [0.50], [0.25, 0.75]]:
             for axis, dim in zip(
                 [None, 0, [0], [0, 1]], [None, "x", ["x"], ["x", "y"]]
             ):
-                actual = self.dv.quantile(q, dim=dim)
+                actual = DataArray(self.va).quantile(q, dim=dim, keep_attrs=True)
                 expected = np.nanpercentile(
                     self.dv.values, np.array(q) * 100, axis=axis
                 )
                 np.testing.assert_allclose(actual.values, expected)
+                assert actual.attrs == self.attrs
 
     def test_reduce_keep_attrs(self):
         # Test dropped attrs