ENH: Group some columns in subplots with DataFrame.plot

[NicolasHug]

df.plot(subplots=True) will create one subplot per column. Is there a way to group multiple columns on the same subplot (and leave the rest of the column separated)?

I'd be happy to submit a PR if that's something you'd consider? In terms of API subplot could accept a list of tuples where each tuple indicates which columns should be grouped together.

[TomAugspurger]

Just to make sure I understand, df.plot(subplots=[('a', 'b'), ('d', 'e', 'f')]) would have two axes?

I'm not sure, but I'm guessing it'd be somewhat complicated to work that into our current subplots logic. At glance, it looks like we assume subplots=True -> one axes per column in several places.

[NicolasHug]

df.plot(subplots=[('a', 'b'), ('d', 'e', 'f')]) would have two axes?

Yes that's the idea. My motivation is that sometimes some columns are comparable, in which case it would make sense to plot them together.