Add broadcast_like.

Closes pydata#2885

Author: dcherian

doc/api.rst

@@ -212,6 +212,7 @@ Reshaping and reorganizing
    Dataset.shift
    Dataset.roll
    Dataset.sortby
+   Dataset.broadcast_like
 
 DataArray
 =========
@@ -386,6 +387,7 @@ Reshaping and reorganizing
    DataArray.shift
    DataArray.roll
    DataArray.sortby
+   DataArray.broadcast_like
 
 .. _api.ufuncs:
 

doc/whats-new.rst

@@ -23,6 +23,8 @@ New functions/methods
 
 - New methods for reshaping Datasets of variables with different dimensions
   (:issue:`1317`). By `Noah Brenowitz <https://github.com/nbren12>`_.
+- Added :py:meth:`DataArray.broadcast_like` and :py:meth:`Dataset.broadcast_like`.
+  By `Deepak Cherian <https://github.com/dcherian>`_.
 
 Enhancements
 ~~~~~~~~~~~~

xarray/core/dataarray.py

@@ -13,7 +13,7 @@
     computation, dtypes, groupby, indexing, ops, resample, rolling, utils)
 from .accessor_dt import DatetimeAccessor
 from .accessor_str import StringAccessor
-from .alignment import align, reindex_like_indexers
+from .alignment import align, broadcast, reindex_like_indexers
 from .common import AbstractArray, DataWithCoords
 from .coordinates import (
     DataArrayCoordinates, LevelCoordinatesSource, assert_coordinate_consistent,
@@ -986,6 +986,18 @@ def sel_points(self, dim='points', method=None, tolerance=None,
             dim=dim, method=method, tolerance=tolerance, **indexers)
         return self._from_temp_dataset(ds)
 
+    def broadcast_like(self, other: Union['DataArray', Dataset]) -> 'DataArray':
+        """Broadcast this DataArray against another Dataset or DataArray.
+        This is equivalent to xr.broadcast(other, self)[1]
+
+        Parameters
+        ----------
+        other : Dataset or DataArray
+            Object against which to broadcast this array.
+        """
+
+        return broadcast(other, self)[1]
+
     def reindex_like(self, other: Union['DataArray', Dataset],
                      method: Optional[str] = None, tolerance=None,
                      copy: bool = True, fill_value=dtypes.NA) -> 'DataArray':

xarray/core/dataset.py

@@ -15,7 +15,7 @@
 from ..coding.cftimeindex import _parse_array_of_cftime_strings
 from . import (alignment, dtypes, duck_array_ops, formatting, groupby,
                indexing, ops, pdcompat, resample, rolling, utils)
-from .alignment import align
+from .alignment import align, broadcast
 from .common import (ALL_DIMS, DataWithCoords, ImplementsDatasetReduce,
                      _contains_datetime_like_objects)
 from .coordinates import (DatasetCoordinates, LevelCoordinatesSource,
@@ -1978,6 +1978,18 @@ def sel_points(self, dim='points', method=None, tolerance=None,
         )
         return self.isel_points(dim=dim, **pos_indexers)
 
+    def broadcast_like(self, other: Union['Dataset', 'DataArray']) -> 'Dataset':
+        """Broadcast this DataArray against another Dataset or DataArray.
+        This is equivalent to xr.broadcast(other, self)[1]
+
+        Parameters
+        ----------
+        other : Dataset or DataArray
+            Object against which to broadcast this array.
+        """
+
+        return broadcast(other, self)[1]
+
     def reindex_like(self, other, method=None, tolerance=None, copy=True,
                      fill_value=dtypes.NA):
         """Conform this object onto the indexes of another object, filling in

xarray/tests/test_dataarray.py

@@ -1239,6 +1239,21 @@ def test_coords_non_string(self):
         expected = DataArray(2, coords={1: 2}, name=1)
         assert_identical(actual, expected)
 
+    def test_broadcast_like(self):
+        original1 = DataArray(np.random.randn(5),
+                              [('x', range(5))])
+
+        original2 = DataArray(np.random.randn(6),
+                              [('y', range(6))])
+
+        expected1, expected2 = broadcast(original1, original2)
+
+        assert_identical(original1.broadcast_like(original2),
+                         expected1.transpose('y', 'x'))
+
+        assert_identical(original2.broadcast_like(original1),
+                         expected2)
+
     def test_reindex_like(self):
         foo = DataArray(np.random.randn(5, 6),
                         [('x', range(5)), ('y', range(6))])

xarray/tests/test_dataset.py

@@ -1560,6 +1560,21 @@ def test_sel(lab_indexer, pos_indexer, replaced_idx=False,
         assert_identical(mdata.sel(x={'one': 'a', 'two': 1}),
                          mdata.sel(one='a', two=1))
 
+    def test_broadcast_like(self):
+        original1 = DataArray(np.random.randn(5),
+                              [('x', range(5))], name='a').to_dataset()
+
+        original2 = DataArray(np.random.randn(6),
+                              [('y', range(6))], name='b')
+
+        expected1, expected2 = broadcast(original1, original2)
+
+        assert_identical(original1.broadcast_like(original2),
+                         expected1.transpose('y', 'x'))
+
+        assert_identical(original2.broadcast_like(original1),
+                         expected2)
+
     def test_reindex_like(self):
         data = create_test_data()
         data['letters'] = ('dim3', 10 * ['a'])