Better names for concat arrays

Author: Zac-HD

doc/whats-new.rst

@@ -74,6 +74,10 @@ Bug fixes
 
 - Silenced warnings that appear when using pandas 0.24.
   By `Stephan Hoyer <https://github.com/shoyer>`_
+- Concatenating a sequence of :py:class:`~xarray.DataArray` with varying names
+  sets the name of the output array to ``None``, instead of the name of the
+  first input array.
+  (:issue:`2775`). By `Zac Hatfield-Dodds <https://github.com/Zac-HD>`_.
 - Interpolating via resample now internally specifies ``bounds_error=False``
   as an argument to ``scipy.interpolate.interp1d``, allowing for interpolation
   from higher frequencies to lower frequencies.  Datapoints outside the bounds

xarray/core/combine.py

@@ -6,6 +6,7 @@
 
 from . import utils
 from .alignment import align
+from .computation import result_name
 from .merge import merge
 from .variable import IndexVariable, Variable, as_variable
 from .variable import concat as concat_vars
@@ -323,16 +324,10 @@ def _dataarray_concat(arrays, dim, data_vars, coords, compat,
         raise ValueError('data_vars is not a valid argument when '
                          'concatenating DataArray objects')
 
-    datasets = []
-    for n, arr in enumerate(arrays):
-        if n == 0:
-            name = arr.name
-        elif name != arr.name:
-            if compat == 'identical':
-                raise ValueError('array names not identical')
-            else:
-                arr = arr.rename(name)
-        datasets.append(arr._to_temp_dataset())
+    name = result_name(arrays)
+    if name is None and compat == 'identical':
+        raise ValueError('array names not identical')
+    datasets = [arr.rename(name)._to_temp_dataset() for arr in arrays]
 
     ds = _dataset_concat(datasets, dim, data_vars, coords, compat,
                          positions)

xarray/tests/test_combine.py

@@ -297,6 +297,16 @@ def test_concat_lazy(self):
         assert combined.shape == (2, 3, 3)
         assert combined.dims == ('z', 'x', 'y')
 
+    def test_concat_names(self):
+        ds = Dataset({'foo': (['x', 'y'], np.random.random((2, 2))),
+                      'bar': (['x', 'y'], np.random.random((2, 2)))})
+        # Concat arrays with different names, new name is None
+        new = concat([ds.foo, ds.bar], dim='new')
+        assert new.name is None
+        # Concat arrays with same name, name is preserved
+        foobar = ds.foo.rename('bar')
+        assert concat([foobar, ds.bar], dim='new').name == 'bar'
+
 
 class TestAutoCombine(object):