BinTransform does not support rangeFormula

[YuhanLu]

In #2360, I didn't add format to support rangeFormula and we might need it in the future.

[YuhanLu]

vega-lite/src/compile/data/bin.ts

Line 25 in 2684aec

const guide = (model instanceof UnitModel) ? (model.axis(channel) || model.legend(channel) || {}) : {};

we require model.axis or model.legend as a guide to get the format from them but in makeBinFromTransform() we are not supposed to deal with encoding at all. The solution for this is to let user specify format in BinTransform and that might involve a lot changes. So we just don't support rangeFormula for now.

[kanitw]

The solution for this is to let user specify format in BinTransform and that might involve a lot changes.

That's one solution but not a good one. The better one is to only add bin _range when we use the bin field in a channel that requires range, but that is trickier and doesn't seem like worth doing now.

[kanitw]

Close as it's a part of #2912