Multiple channels in single mark

[vwkd]

How can I use multiple channels in a single mark?

For example, I'm trying to plot multiple series each over multiple years in a single plot.

const data = [
  { x: 0, y: 0, year: 2000, species: "dog" },
  { x: 5, y: 2, year: 2000, species: "dog" },
  { x: 0, y: 0, year: 2001, species: "dog" },
  { x: 5, y: 3, year: 2001, species: "dog" },
  // ... more years
  { x: 0, y: 0, year: 2000, species: "cat" },
  { x: 5, y: 4, year: 2000, species: "cat" },
  { x: 0, y: 0, year: 2001, species: "cat" },
  { x: 5, y: 5, year: 2001, species: "cat" },
  // ... more years
  // ... more species
];

I could use different marks but this doesn't scale.

Plot.plot({
  document,
  color: { legend: true },
  marks: [
    Plot.line(data, {
      filter: d => d.year === 2000,
      x: "x",
      y: "y",
      stroke: "species",
    }),
    Plot.line(data, {
      filter: d => d.year === 2001,
      x: "x",
      y: "y",
      stroke: "species",
    }),
    // ... more years
  ],
});

I tried to use stroke and z together, however it seems z is not applied.

Plot.plot({
  color: { legend: true },
  marks: [
    Plot.line(data, {
      x: "x",
      y: "y",
      stroke: "species",
      // todo: somehow this doesn't apply
      z: "year",
    }),
  ],
});

Is this a known limitation? What's the best approach here?

[Fil]

z should identify individual series, in this case probably something like:

z: (d) => `${d.year} ${d.species}`