issues

What happened?

Please see code below

With xarray:2022.06.0, DataArray.unstack raise an ValueError exception

```python-traceback

ValueError Traceback (most recent call last) Input In [2], in <cell line: 24>() 21 y = y.assign_coords(day=y.j + y.last_j) 22 y = y.set_index(multi=['sub_id', 'last_j']) ---> 24 y = y.unstack()

File /opt/conda/lib/python3.9/site-packages/xarray/core/dataarray.py:2402, in DataArray.unstack(self, dim, fill_value, sparse) 2342 def unstack( 2343 self, 2344 dim: Hashable | Sequence[Hashable] | None = None, 2345 fill_value: Any = dtypes.NA, 2346 sparse: bool = False, 2347 ) -> DataArray: 2348 """ 2349 Unstack existing dimensions corresponding to MultiIndexes into 2350 multiple new dimensions. (...) 2400 DataArray.stack 2401 """ -> 2402 ds = self._to_temp_dataset().unstack(dim, fill_value, sparse) 2403 return self._from_temp_dataset(ds)

File /opt/conda/lib/python3.9/site-packages/xarray/core/dataset.py:4656, in Dataset.unstack(self, dim, fill_value, sparse) 4652 result = result._unstack_full_reindex( 4653 dim, stacked_indexes[dim], fill_value, sparse 4654 ) 4655 else: -> 4656 result = result._unstack_once( 4657 dim, stacked_indexes[dim], fill_value, sparse 4658 ) 4659 return result

File /opt/conda/lib/python3.9/site-packages/xarray/core/dataset.py:4492, in Dataset.unstack_once(self, dim, index_and_vars, fill_value, sparse) 4489 else: 4490 fill_value = fill_value -> 4492 variables[name] = var.unstack_once( 4493 index=clean_index, 4494 dim=dim, 4495 fill_value=fill_value, 4496 sparse=sparse, 4497 ) 4498 else: 4499 variables[name] = var

File /opt/conda/lib/python3.9/site-packages/xarray/core/variable.py:1732, in Variable._unstack_once(self, index, dim, fill_value, sparse) 1727 # Indexer is a list of lists of locations. Each list is the locations 1728 # on the new dimension. This is robust to the data being sparse; in that 1729 # case the destinations will be NaN / zero. 1730 data[(..., *indexer)] = reordered -> 1732 return self._replace(dims=new_dims, data=data)

File /opt/conda/lib/python3.9/site-packages/xarray/core/variable.py:985, in Variable._replace(self, dims, data, attrs, encoding) 983 if encoding is _default: 984 encoding = copy.copy(self._encoding) --> 985 return type(self)(dims, data, attrs, encoding, fastpath=True)

File /opt/conda/lib/python3.9/site-packages/xarray/core/variable.py:2720, in IndexVariable.init(self, dims, data, attrs, encoding, fastpath) 2718 super().init(dims, data, attrs, encoding, fastpath) 2719 if self.ndim != 1: -> 2720 raise ValueError(f"{type(self).name} objects must be 1-dimensional") 2722 # Unlike in Variable, always eagerly load values into memory 2723 if not isinstance(self._data, PandasIndexingAdapter):

ValueError: IndexVariable objects must be 1-dimensional ```

What did you expect to happen?

Please see code below

With xarray:2022.03.0, code runs well

Minimal Complete Verifiable Example

```Python import xarray as xr import numpy as np

x = np.concatenate((np.repeat(np.nan,4), np.repeat(1,2))).reshape(3, 2).transpose() x = xr.DataArray( x, coords = { 'composite_id': ['s00', 's10'], 'sub_id': ('composite_id', ['0', '1']), 'last_j': ('composite_id', [100, 111]), 'j': [-2,-1,0] }, dims= ['composite_id', 'j'] )

y = x y = y.stack({'multi': ['composite_id', 'j']}) y = y.dropna('multi') y = y.assign_coords(day=y.j + y.last_j) y = y.set_index(multi=['sub_id', 'last_j'])

y = y.unstack() ```

MVCE confirmation

• [X] Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• [X] Complete example — the example is self-contained, including all data and the text of any traceback.
• [X] Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• [x] New issue — a search of GitHub Issues suggests this is not a duplicate.

Relevant log output

No response

Anything else we need to know?

No response

Environment

Not working environment with xarray 2022.06.0

Working environment with xarray 2022.03.0