Alternative scale zero property (in addition to true or false)

[kanitw]

From https://twitter.com/Datawrapper/status/1070702878061416448,

I could see we extend the scale's zero property with an object describing automatic criteria such as maximum % that could be added.

@jheer -- I wonder where is the logic for reading scale's zero and adding it to the domain in the codebase? (I searched for "zero" in vega-scale and vega-parser but couldn't find one.)

[domoritz]

Couldn't you just write an expression that determines the domain based on how far away it is from zero?

[jheer]

Yes you could! Here is an editor example, with a 0.24 threshold chosen so that one axis adjusts to zero and the other doesn't.

Vega-Lite could generate code like this if desired. That said, in Vega people probably do not want to add new extent transforms and signal definitions. One option would be to update the zero directive to also accept a number indicating a percentage threshold. This would require updating the Scale transform in vega-encode and also the schema definition.

[kanitw]

Would the monorepo in #1472 land any time soon?

If I have time over the holiday break, I might try to fix this. :)

[jheer]

Yes, I plan to merge the monorepo to master sometime in the next week. Everything is working, just want to double check everything and update the documentation / README.md files.

[kanitw]

Ah I was playing with this and found this issue. (FWIW, this is a similar Vega-Lite spec for playing with the threshold)

cc: @yhoonkim