How do I transform tick labels without explicitly specifying breaks?

Let’s say I have a scatter plot where the x-axis date is pandas.Timestamp objects. By default, plotnine renders the x tick labels on my plot such such that they run into each other.

I’d like to do an arbitrary transformation on the x-axis tick labels. For example, I’d like the tick labels to be blank except for the first day of the year, in which case I want the tick label to just be the year, so "2017-03-04" would transform to "", and "2016-01-01" would transform to "2016".

However, I don’t want to explicitly specify the breaks. Instead, I want plotnine to use its default algorithm for determining where to put the breaks.

Is this possible to do with plotnine?

[has2k1]

Re-opened to serve as a reminder for a tutorial section on date labels and breaks.

[lorin]

That’s pretty close, but not quite what I wanted. However, it did help me figure out what I really wanted was this:

+ scale_x_datetime(labels=lambda lst: [x.year if x.month==1 and x.day==1 else "" for x in lst])

As an aside, the scale docs describe the labels argument as a list, specifically:

labels (list, optional) – List of str. Labels at the breaks.

However, given the answer above, it appears that the labels argument can also be a callable that takes a list (array_like?) of breakpoints as input and returns a list of strings as output.

Should the docs be updated? If so, I’m willing to submit a PR.