Color by qualitative variable

[bhogan-mitre]

It would be nice to be able to color by a qualitative variable. For example, in the dev app scatter plot when selecting color by months, the points change from default blue to black (all taking the same color).

It seems this may be a limitation in the underlying plotly.js. But the user isn't going to know that as they are presented an option to color by that field.

I'm not sure the best way to approach this. Is it dependent on the 'split by' transform being plugged in? Or is there a way to map that qualitative variable to a numeric index behind the scenes? The latter seems easier for the user, but it may be challenging/impossible to get a legend to communicate what the colors correspond to in that case.

[nicolaskruchten]

Right now the only way to do this is with the groupby/splitby transform, but I'd love for plotly.js to get builtin support for just color-by-category. It wouldn't be hard to get basic support for it: just map categories to numbers and reuse the existing colorbar system but the complexities of configuration will add up quickly: how to control the order of the colors, the specific mapping of color to category, the difference between colorbar and legend behaviour etc. The groupby transform is clunkier to use initially but gives essentially all of this control, which is nice.

[bhogan-mitre]

Great, thanks for the info!

[nicolaskruchten]

We'll be taking this up in plotly/plotly.js#1747 and once done there we'll add support here... Closing for now.