add test_stackplot in test_datetime.py #27114
Conversation
There was a problem hiding this comment.
Thank you for opening your first PR into Matplotlib!
If you have not heard from us in a week or so, please leave a new comment below and that should bring it to our attention. Most of our reviewers are volunteers and sometimes things fall through the cracks.
You can also join us on gitter for real-time discussion.
For details on testing, writing docs, and our review process, please see the developer guide
We strive to be a welcoming and open project. Please follow our Code of Conduct.
There was a problem hiding this comment.
I think this has also uncovered that stackplot doesn't quite work as intended for unitful data (which is good, that is why we want these tests, to be clear)
I'll try to write up an issue later about it, but the thing that is throwing alarm bells to me is this line:
matplotlib/lib/matplotlib/stackplot.py
Line 81 in 978b402
The promote_types call there actually works for datetimes passed as object arrays (which is why this test works at all), but will fail for np.datetime64 arrays (which we should either make work and add to this test or be clear about it not working....) I think that datetimes are a bit of an edge case here, but the broader point about units and that promote_types call could be problematic...
| [datetime.datetime(2023, 1, i) for i in range(1, N)] | ||
| ) | ||
| dates_years = np.array( | ||
| [datetime.datetime(1970 + i, 1, 1) for i in range(1, N)] |
There was a problem hiding this comment.
I would avoid this date, as 1970 can hide problems where we don't actually convert dates properly.
(You are actually avoiding the most likely problematic year by starting at 1, but it is still close enough to throw some alarm bells off)
| ) | ||
| ax2.set_ylim( | ||
| datetime.datetime(2022, 12, 31), | ||
| datetime.datetime(2023, 2, 8) | ||
| ) |
There was a problem hiding this comment.
These limits are hiding the fact that the blue section goes all the way to 1970 because of the implicit 0 of stackplot.
I would support extending the API of the baseline kwarg to accept a scalar value, but that is not how it is implemented now, and I think that is out of the scope of this PR.
As it stands, I think I would rather not test the "timedelta on the y axis" case than provide this test which is not a sensible use of datetime (though I think it is not far off, and you made something that looked okay... I just think that the tools are not there to make using datetimes sensible here)
I do think timedelta is the right unit for this plot, to be clear... just it needs that extra explicit baseline, which is not currently supported (only zero or the various "wiggle" type options are supported currently)
|
Thanks for the review. I changed the starting year in the first test to 2020 from 1971. I also removed the second test until the baseline issue is addressed. Just double-checking for the second test -- was the only problem the inability to set an explicit baseline, or were there other issues with how it was written? |
|
I think the inability to set a baseline was the only problem for I think that there could be some debate on whether the y axis of this plot should even be a concrete date (rather it is always an offset, perhaps), but we don't actually have handling for that built in yet... Again, those shortcomings are of the current implementation, which while being not quite fully broken, is lacking polish, not of the test you wrote. |
|
Hi @QuLogic, I have made the changes you suggested. |
|
Thanks @QuadroTec! Congratulations on your first PR to Matplotlib 🎉 We hope to hear from you again. |
|
Thank you @QuLogic! |
PR summary
Adds the test_stackplot method in test_datetime.py. The test creates the following stackplots:
datetimex-axis, stacked numerical y-axisdatetimex-axis,datetimeplus stackeddatetime.timedeltay-axisStacking multiple
datetimearrays caused a compile error, because numpy does not support adding twodatetimeobjects together. I don't believe it makes much sense to stackdatetimevalues in this way, so I have not implemented this test.This pull request closes the
Axes.stackplottask in issue #26859Plot output
PR checklist
Axes.stackplotin #26864