BUG: Make secondary_y work properly for bar plots GH3598

[danbirken]

As far as I'm aware this seems to work properly, but I'm not sure if this was done the previous way for a reason I don't understand.

Fixes: #3598

[cpcloud]

can u add release notes?

[danbirken]

Done

[cpcloud]

@jreback looks ok 2 me, thoughts?

[jreback]

is mark_right a public option?

[danbirken]

In a theoretical sense they should be public, in the spirit of this option being similar to "stacked" for bar plots or the same properly "mark_right" for a LinePlot; it is a perfectly reasonable publicly editable properly of a plot.

However, since via standard use of (series|frame).plot(kind='xyz'), you never actually get to interact with the XyzPlot object (and nowhere else in the pandas codebase are these plot objects ever interacted with) I don't think it matters all that much, and since there already is a previous convention I believe sticking with that is reasonable.

[jreback]

that's all fine
didn't know if they belong in the doc string

[danbirken]

I just added it to the docstring of plot_frame() [along with fixing minor mistake in secondary_y]. It is getting a little verbose, but more documentation is probably better than less in general. Up to you.

[jreback]

that looks good thxs

[jreback]

thanks!