sort when encoding coordinates for deterministic outputs #8034
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itcarroll
changed the title
dcherian
reviewed
Aug 1, 2023
headtr1ck
approved these changes
Aug 3, 2023
Co-authored-by: Michael Niklas <[email protected]>
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whats-new.rst[ ] New functions/methods are listed inapi.rstThe PR changes
conventions._encode_coordinatesto addsortedduring the creation of "coordinates" strings de novo. It does not touch user-specified coordinates attributes or encodings.The PR adds a test, but also changes two pre-existing tests that allowed for non-deterministic ordering of the coordinates string.
In reviewing the netCDF data model and CF convenstions, I confirmed that there is no requirement on the ordering of names in the coordinates attribute. I also learned that the global coordinates attribute created by XArray for non-dimension coordinates that are not associated with a variable is not compliant with CF conventions, as was discussed in 2014. In 2021, CF-Conventions 1.9 added "Domain Variables", which appear to provide a CF compliant way to handle this situation. I will likely open an enhancement issue to weigh making that change.