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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Deprecate plot_date()","articleBody":"*This is a writeup / proposal to serve as a basis for discussion in the dev call on 03 Aug 2020.*\r\n\r\n`plot_date()` is essentially a thin wrapper around `plot()` but has different defaults for `fmt`. This causes confusion #17548, #18141.\r\n\r\n### Context\r\n\r\n- **Use case:** `plot_date()` dates back way before Matplotlib supported units. It's nowadays only necessary if you have plain numbers (in matplotlibs epoch). `datetime`s are directly handled in `plot()` via the unit system.\r\nWhile there may be users for `plot_date()`, i suppose it's rather a niche application.\r\n\r\n- **Naming:** The name is a bit misleading in that it suggests that you should use the function if you want to plot dates. This implicitly includes `datetime` / `date` which would be misleading. I'm suspecting that it may lead users with `datetime`/`date` objects on the wrong track. (`plot_as_date()` would have been more appropriate, but we're not gonna change that).\r\n\r\n- **API design:** `plot_date()` is an ad-hoc aggregation of `plot()` and `axis_date()`\r\n  ~~~\r\n    def plot_date(self, x, y, fmt='o', tz=None, xdate=True, ydate=False, **kwargs):\r\n        if xdate:\r\n            self.xaxis_date(tz)\r\n        if ydate:\r\n            self.yaxis_date(tz)\r\n        return self.plot(x, y, fmt, **kwargs)\r\n  ~~~ \r\n\r\n\r\n### Recommendation\r\nGiven the above context, I propose to deprecate `plot_date()` in favor of `ax.plot()` and `ax.x/yaxis.axis_date()`.\r\n\r\nAt the same time, deprecate `ax.x/yaxis_date()` in favor of `ax.x/yaxis.axis_date()`. This reduces the API footprint of `Axes`. IMHO we don't need to have wrappers `x/yfoo()` wrappers for every `foo()` function on the axis. While common ones like `set_x/ylabel()` have a justification, it's fine in general to use `ax.xaxis.foo()`.\r\n\r\n#### Alternatives:\r\n\r\n- Keep as is - I wouldn't do that as it's confusing users.\r\n- Change the default `fmt` to match `plot()` - Such a default change requires as much user action as the deprecation, but we keep all the unnecessary redundancy / imperfect naming.\r\n- Only soft-deprecate (i.e. add a note to discourage the use but keep the function). This would be an option if we're strongly concerned with not forcing users to change their `plot_date()` code.","author":{"url":"https://github.com/timhoffm","@type":"Person","name":"timhoffm"},"datePublished":"2020-08-02T16:06:18.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":6},"url":"https://github.com/18154/matplotlib/issues/18154"}