Skip to content

Bug in broadcasting with multi-indexes #6430

Closed
@dcherian

Description

@dcherian

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

Metadata

Metadata

Assignees

No one assigned

    Type

    No type

    Projects

    No projects

    Milestone

    No milestone

    Relationships

    None yet

    Development

    No branches or pull requests

    Issue actions