Refactor Repeat as a Macro?

[domoritz]

Our repeat should have the same behavior as using fold (unpivot) and then facet into row/column. We should investigate whether it makes sense to clean up the implementation and implement repeat as a macro.

[kanitw]

Implementing repeat as a macro of concat (not facet) might be reasonable.

However, making repeat = pivot + facet is extremely unintuitive and would produce unnecessary data transforms, so it definitely should NOT be done.

Also, I don't think this is a "help wanted" issue since it's not even clear that it should be done. It's also not an "enhancement" to the language, but rather internal refactor.

[domoritz]

However, making repeat = pivot + facet is extremely unintuitive and would produce unnecessary data transforms, so it definitely should NOT be done.

I don't know how bad the produced code would be. Therefore I'm not sure I agree.

[domoritz]

A related enhancement of Vega-Lite would be having something like repeat but for layering. The idea would be that you can make for example a multi-series line chart with three lines (A to C) for a dataset with columns time, A, B, and C. @tvst was asking for something like this in Altair.

[jheer]

Though I find the notion of repeat = fold + facet conceptually appealing (I don't think you mean pivot?), I should point out that using Vega's current implementation such an approach might induce a lot of additional, unnecessary processing and memory overhead.

[kanitw]

A related enhancement of Vega-Lite would be having something like repeat but for layering. The idea would be that you can make for example a multi-series line chart with three lines (A to C) for a dataset with columns time, A, B, and C. @tvst was asking for something like this in Altair.

See #1274 and #1552 for existing issues.

[domoritz]

I don't think you mean pivot?

You are right, I meant unpivot or fold.

[kanitw]

pretty much done in #6002, pending a few minor issues left.