ENH: Improve plotting types

[bashtage]

Add types for many inputs
Clean out non-public functions

• Tests added: Please use assert_type() to assert the type of any return value

[Dr-Irv]

Might be good in the tests to have one test where we test all the kwargs documented in DataFrame.plot()

[Dr-Irv]

I think all of the keywords in DataFrame.plot() can also be passed to things like DataFrame.plot.line(), etc. So I think we should copy the keywords you included in __call__() over to each of the individual functions. E.g., the following is valid:

foo = pd.DataFrame({"x":[i for i in range(10)], "y":[i*i for i in range(10)]})
foo.plot.line("x", "y", figsize=(3,3))

You don't have to test each one.

[bashtage]

I think all of the keywords in DataFrame.plot() can also be passed to things like DataFrame.plot.line(), etc. So I think we should copy the keywords you included in __call__() over to each of the individual functions. E.g., the following is valid:

I'm hesitant to do this since not all keywords are accepted by all plot types and some, even if accepted, have no effect. For example, positions and colorbar can't be used with line. IMO, the general plot() function is a mess of a function but is there for quick analysis.

[Dr-Irv]

I'm hesitant to do this since not all keywords are accepted by all plot types and some, even if accepted, have no effect. For example, positions and colorbar can't be used with line. IMO, the general plot() function is a mess of a function but is there for quick analysis.

Fair point. It's not clear to me if people would do df.plot(x="x", y="y", kind="line", figsize=(5, 5)) or df.plot.line(x="x", y="y", figsize=(5, 5)), although the examples at https://pandas.pydata.org/docs/user_guide/visualization.html?highlight=plotting seem to show the latter usage. Having said that, I think many of the accepted keywords listed in DataFrame.plot() in the docs are potentially specific to the chosen backend, so getting that right from a typing perspective would be a nightmare.

[Dr-Irv]

thanks @bashtage