Clarify impact of datetime coordinate unit on `polyfit`, `polyval`, `integrate`, `differentiate`
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Description
What is your issue?
We will soon support non-nanosecond time units. There are a few functions whose output could rely on the spacing of coordinate values: polyfit , polyval, integrate, differentiate (are there any more?)
integrateanddifferentiatetake adatetime_unitkwarg,polyfitandpolyvaldo not.polyfitandpolyvalforce conversion tons: https://github.com/pydata/xarray/blob/ceb5364be999567d08ba9be832fa0440e6dd3407/xarray/core/computation.py#L2117
We probably want to relax (2) in the future. Either way it would be good to systematically think about this and at least talk about it in the docstrings.
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First steps
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Research direction
Start in xarray/core/computation.py around the polyfit and polyval conversion referenced in the issue, then inspect the documented behavior of polyfit, polyval, integrate, and differentiate. Determine whether their datetime-unit effects are described consistently and document the agreed behavior for each function, including any additional affected functions identified during review.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- python
- Domain
- data
- Issue type
- Documentation
- Difficulty
- 4/5
- Estimated time
- 3-5 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 35/100