Extension of plot interface to errorbar plots

[aimpertro]

It would be amazing to have a possibility to marry the plotting interface for DataArrays with the "group by" operations. Specifically, I often find myself wanting to create an errorbar plot using matplotlib. The data points come from a DataArrayGroupby.mean() call, and the yerrors from DataArrayGroupby.std(). I then create the plot manually as I cannot make use of xarray's matplotlib wrapper.

I would like to extend the mpl wrapper to allow that in a single call. What would be the best strategy to do that?

I personally was thinking about adding a plot() function to core.groupby.DataArrayGroupBy, where one can specify which reduction operation is used for which plot parameter (e.g. ydata as 'mean', yerr as 'std'). But this might be a bit narrow in terms of usability, so I'm open for some feedback.

Thanks for your input!