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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"[ENH]: Better support for stackplot with units [particularly datetimes]","articleBody":"### Problem\r\n\r\nAs noted during the review of #27114, the current support of units in stackplot is subpar, particularly for the `y` axis.\r\n\r\nFor datetimes in particular, the implicit 0 of the API is problematic, introducing 1970-01-01 when that is not a relevant date.\r\n\r\nTherefore I suggest allowing `baseline` to be not only the current supported string literals, but also a scalar value (or potentially an array, I guess) such that a \"sensible\" baseline can be provided for cases where `0` is not sensible. (even the other options for baseline assume you want your plot centered around 0... I'm not concerned about wanting \"wiggle centered at 2023-02-28\" or anything like that, that seems perhaps a bridge too far.)\r\n\r\nI also think it is important to explicitly state that the y values are in delta units (similar to how we do for e.g. [`bar`](https://matplotlib.org/stable/api/_as_gen/matplotlib.axes.Axes.bar.html#matplotlib.axes.Axes.bar) for the `width` parameter. This is already true in that adding actual datetime values will fail, but passing timedelta objects will work.\r\n\r\nFinally, the `cumsum` call contains a `promote_types(y.dtype, np.float32)`, which will fail for `np.timedelta64` arrays (Edit, to be consistent with other points, clarified that I really meant timedelta instead of datetime64 here):\r\n\r\nhttps://github.com/matplotlib/matplotlib/blob/39582424f8ce5e042e4e39eeac94893f222c9f8b/lib/matplotlib/stackplot.py#L81\r\n\r\nSo either removing that or at least handling the error case is needed. It's not fully clear to me what we are guarding against there, as `cumsum` of integers is fine being integral, though I guess we _could_ run into overflow issues? Passing `datetime.timedelta` as `object` arrays (or as lists which get turned into `object` arrays) will work and produce _a_ plot, just without a sensible baseline, currently. \r\n\r\n### Proposed solution\r\n\r\n_No response_","author":{"url":"https://github.com/ksunden","@type":"Person","name":"ksunden"},"datePublished":"2023-10-17T22:44:15.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/27129/matplotlib/issues/27129"}