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Bug in broadcasting with multi-indexes #6430
Description
What happened?
import numpy as np
import xarray as xr
ds = xr.Dataset(
{"foo": (("x", "y", "z"), np.ones((3, 4, 2)))},
{"x": ["a", "b", "c"], "y": [1, 2, 3, 4]},
)
expected = ds.sum("z")
stacked = ds.stack(space=["x", "y"])
broadcasted, _ = xr.broadcast(stacked, stacked.space)
stacked.sum("z").unstack("space") # works
broadcasted.sum("z").unstack("space") # error---------------------------------------------------------------------------
ValueError Traceback (most recent call last)
Input In [13], in <module>
10 broadcasted, _ = xr.broadcast(stacked, stacked.space)
11 stacked.sum("z").unstack("space")
---> 12 broadcasted.sum("z").unstack("space")
File ~/work/python/xarray/xarray/core/dataset.py:4332, in Dataset.unstack(self, dim, fill_value, sparse)
4330 non_multi_dims = set(dims) - set(stacked_indexes)
4331 if non_multi_dims:
-> 4332 raise ValueError(
4333 "cannot unstack dimensions that do not "
4334 f"have exactly one multi-index: {tuple(non_multi_dims)}"
4335 )
4337 result = self.copy(deep=False)
4339 # we want to avoid allocating an object-dtype ndarray for a MultiIndex,
4340 # so we can't just access self.variables[v].data for every variable.
4341 # We only check the non-index variables.
4342 # https://github.com/pydata/xarray/issues/5902
ValueError: cannot unstack dimensions that do not have exactly one multi-index: ('space',)
What did you expect to happen?
This should work.
Minimal Complete Verifiable Example
No response
Relevant log output
No response
Anything else we need to know?
No response
Environment
xarray main after the flexible indexes refactor
Activity
benbovy commentedon Apr 2, 2022
Probably because we still need some internal refactoring in
xr.broadcast(added in #6293).spaceandx/yshould all have identicalPandasMultiIndexobjects but they don't.Propagate MultiIndex variables in broadcast
Propagate MultiIndex variables in broadcast