The areaY mark’s interval option doesn’t work with y1 and y2

[mbostock]

The maybeDenseIntervalX transform used by areaY’s interval option uses the binX transform, but only outputs the y channel:

plot/src/transforms/bin.js

Line 70 in 194e1f4

: bin({[k]: options?.reduce === undefined ? reduceFirst : options.reduce, filter: null}, options);

This means it doesn’t work if the areaY mark is using the y1 and y2 options:

Plot.areaY(aapl.slice(0, 81), {
  x: "Date",
  y1: "Low",
  y2: "High",
  interval: "day",
  curve: "step"
}).plot()

It should instead be equivalent to this:

Plot.areaY(
  aapl.slice(0, 81),
  Plot.binX(
    { y1: "first", y2: "first", filter: null },
    { x: "Date", y1: "Low", y2: "High", interval: "day", curve: "step" }
  )
).plot()

So somehow maybeDenseIntervalX will need to know to output y1 and y2 instead.

Ref. https://observablehq.com/d/39a059b4b6322d37