How to aggregate other channels when grouping?

[mbostock]

This works, the definition of the text channel is awkward:

Plot.plot({
  marks: [
    Plot.barX(penguins, Plot.stackX(Plot.groupZX({fill: "species", normalize: true}))),
    Plot.text(penguins, Plot.stackXMid(Plot.groupZX({text: ([d]) => d.species, z: "species", normalize: true}))),
    Plot.ruleX([0, 100])
  ]
})

I’d prefer something like this:

Plot.plot({
  marks: [
    Plot.barX(penguins, Plot.stackX(Plot.groupZX({fill: "species", normalize: true}))),
    Plot.text(penguins, Plot.stackXMid(Plot.groupZX({text: "species", z: "species", normalize: true}))),
    Plot.ruleX([0, 100])
  ]
})

But this would require that the group transform know that text is a channel, and to aggregate it (by selecting the first value, presumably). And currently the group transform doesn’t need to know how to interpret the passed-in options, other than the ones that are specifically eligible for grouping (namely x, y, z, fill, stroke).

[Fil]

text and title should be eligible to Z?

[mbostock]

Fixed in #272.

[oluckyman]

Just for the reference put an up to date working example here (as I landed on this issue while googling for an example of labelling sections on a stacked bar chart)

Plot.plot({
  marks: [
    Plot.barX(
      dtDiagnostics,
      Plot.groupY({ x: "count" }, { y: "subject", fill: "class" })
    ),
    Plot.text(
      dtDiagnostics,
      Plot.stackX(
        Plot.groupY(
          { x: "count" },
          { y: "subject", z: "class", fill: "white", text: (d) => d[0].class }
        )
      )
    )
  ],
  marginLeft: 100
})