Sense categorical data

[yelper]

This feature is a little open-ended...

Discover ways of sensing categorical data. With this knowledge, components can treat these fields differently (e.g a scatterplot using a categorical data as an axis will revert to a dot-plot for that axis, a dropdown will become a slider, a multiselect would become a interval slider, etc.).

Experiment how best to expose this abstraction to the user, including making internal decisions obvious to the developer through an abstraction so that heuristic issues can be rectified manually in an ad-hoc manner. Bugs pertaining to this logic should reference this issue.

[yelper]

Mike's suggestion: think of ways that people misuse scatterplots and guide them away from their decisions (e.g. comparing distributions of different series will turn into a dot plot where one axis is categorical).

See http://bl.ocks.org/armollica/0f28622e38434b04907d768df6cec684 for some ideas.