pydata / pydata/xarray

DataArray.transpose with transpose_coords=True does not change coords order

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contrib-help-wanted enhancement needs discussion
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Python
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Description

What happened?

I used DataArray.transpose with transpose_coords=True to change the coords order from
startings_dims = "dim_0", "dim_1", "dim_2"
to
reordered_dims = "dim_2", "dim_1", "dim_0".

The order of dims was correctly transposed but the order of coords remained unchanged.

What did you expect to happen?

I expected the transposed coords to be in the new order:

reordered_dims = "dim_2", "dim_1", "dim_0"

Minimal Complete Verifiable Example
import numpy as np
import pandas as pd
import xarray as xr

np.random.seed(0)
temperature = np.random.randn(4, 4, 3)
dim_0_values = [1, 2, 3, 4]
dim_1_values = [5, 6, 7, 8]
dim_2_values = pd.date_range("2014-09-06", periods=3)
starting_dims = "dim_0", "dim_1", "dim_2"

da = xr.DataArray(
    data=temperature,
    dims=starting_dims,
    coords=dict(
        dim_0=dim_0_values,
        dim_1=dim_1_values,
        dim_2=dim_2_values,
    ),
    attrs=dict(
        description="Ambient temperature.",
        units="degC",
    ),
)

print(f"{da.dims=}")
print(f"{da.coords.keys()=}")

reordered_dims = "dim_2", "dim_1", "dim_0"
print(f"{da.transpose(*reordered_dims).dims=}")
print(f"{da.transpose(*reordered_dims).coords.keys()=}")
print(f"{da.transpose(*reordered_dims, transpose_coords=True).coords.keys()=}")
MVCE confirmation
  • Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
  • Complete example — the example is self-contained, including all data and the text of any traceback.
  • Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
  • New issue — a search of GitHub Issues suggests this is not a duplicate.
Relevant log output
da.dims=('dim_0', 'dim_1', 'dim_2')
da.coords.keys()=KeysView(Coordinates:
  * dim_0    (dim_0) int32 1 2 3 4
  * dim_1    (dim_1) int32 5 6 7 8
  * dim_2    (dim_2) datetime64[ns] 2014-09-06 2014-09-07 2014-09-08)
da.transpose(*reordered_dims).dims=('dim_2', 'dim_1', 'dim_0')
da.transpose(*reordered_dims).coords.keys()=KeysView(Coordinates:
  * dim_0    (dim_0) int32 1 2 3 4
  * dim_1    (dim_1) int32 5 6 7 8
  * dim_2    (dim_2) datetime64[ns] 2014-09-06 2014-09-07 2014-09-08)
da.transpose(*reordered_dims, transpose_coords=True).coords.keys()=KeysView(Coordinates:
  * dim_0    (dim_0) int32 1 2 3 4
  * dim_1    (dim_1) int32 5 6 7 8
  * dim_2    (dim_2) datetime64[ns] 2014-09-06 2014-09-07 2014-09-08)
Anything else we need to know?

No response

Environment

INSTALLED VERSIONS

commit: None
python: 3.9.12 (main, Apr 4 2022, 05:22:27) [MSC v.1916 64 bit (AMD64)]
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 85 Stepping 7, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: ('English_United States', '1252')
libhdf5: 1.10.6
libnetcdf: None

xarray: 2022.6.0
pandas: 1.4.2
numpy: 1.21.5
scipy: 1.9.3
netCDF4: None
pydap: None
h5netcdf: None
h5py: 3.6.0
Nio: None
zarr: 2.13.2
cftime: None
nc_time_axis: None
PseudoNetCDF: None
rasterio: None
cfgrib: None
iris: None
bottleneck: 1.3.4
dask: 2022.02.1
distributed: 2022.2.1
matplotlib: 3.5.1
cartopy: None
seaborn: 0.11.2
numbagg: None
fsspec: 2022.02.0
cupy: None
pint: None
sparse: None
flox: None
numpy_groupies: None
setuptools: 61.2.0
pip: 22.3.1
conda: 4.12.0
pytest: 7.1.1
IPython: 8.2.0
sphinx: 4.4.0

Contributor guide

Open the contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by reproducing the reported behavior with the DataArray.transpose entry point and the provided minimal example. Read the transpose_coords behavior in the linked DataArray.transpose documentation and implementation, then verify that the coordinate key order matches the requested dimension order when the issue is fixed.

Written by the indexing model from the issue text.

Assessment

Tech stack
numpy, pandas, python
Domain
data
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Stale
Clarity
Mostly clear
Newbie friendliness
42/100

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