Add control features to metric plots

[romanlutz]

Is your feature request related to a problem? Please describe.

The metric plotting functionality mentioned in the docs does not mention control_features

Describe the solution you'd like

Add an example where control_features are used. In the same example we could use age as a control feature. However, whenever #793 is completed we should switch to the synthetic dataset. After all, it's not ideal to use a real dataset for an abstract purpose of showing this functionality.

Bonus

Ideally, a separator line between the control groups or a new line for each set of subgroups within a control group would be nice. Right now they're all treated as equal groups in the plots.

[bram49]

Hi @romanlutz, I would like to pick this up

[romanlutz]

Sure thing, @bram49 ! To be quite honest, I'm not entirely sure where this will lead. You can play around with the samples we have in the documentation https://fairlearn.org/main/user_guide/assessment.html#plotting-grouped-metrics and see if there's a good way to showcase the control features.

You can basically do the same thing with control features as with sensitive features since the by_group result is just the same kind of DataFrame. The difference comes only through aggregation which isn't really shown. Instead of showing the bars for all groups next to each other I was just wondering whether we could have some kind of separation between the control groups. It's probably not doable with a single command like we have it in the docs linked above, because you'd need to call additional plotting commands. Perhaps the plotting code @alexquach is adding in #857 can be extended to add separators between the groups. In any case, we may just come out of this exploration with the decision not to do anything special (and that's perfectly fine!). If you want to do something more well-defined I'd suggest #666. I can walk you through what's been done on that before since I pair-programmed with @rishabhsamb on that. Just let me know what you think now that I've shared some of my thoughts 🙂

[bram49]

Thanks for the fast and thorough reply!
I will dive into this when #896 is finished. Think I will start with creating the separation lines and see if this will look nice.
If it would not work out I will take a look at #666.