should i be relative to the internal flattened array?

[leeoniya]

right now the public API is split into x and y sections, but internally they're merged to keep the loops uniform, with just a sprinkling of if (i ==0) branching to split off x.

the public API accepts i that is against the internal flattened array, but this is not terribly intuitive, especially since uPlot goes to additional lengths to make it look like the internals match the externals, e.g.

uPlot/src/Line.js

Line 174 in 589d1dd

self.series = splitXY(series);

this can probably be improved.

i've considered dropping the x/y and simply making the lists flat but it results in awkwardness elsewhere. e.g. x is required, but if nothing needs to be customized for the x axis, you need to provide options that start with null: axes: [null, {values}]. also, there can be multiple x axes (let's say different units), then what?

i guess one route can be to attach an extra required property to each option item in a flat list, eg. dir: 'x', but that's not great either.

considerations:

• data[0] is always the x-series data and there can only be a single x series
• there could be multiple x axes (alt units)

if we simply disallow multiple x axes, then this whole situation becomes easier. we can use flat lists and simply say that data[0], series[0] and axes[0] are all x, everything else is y, and then we just use a flat i as we do now and everything becomes logically aligned. yes, there will be axes: [null, {}, {}] but it's easy to reason about.

[leeoniya]

...but multiple x axes can actually be quite useful, especially when comparing 2 time periods, or group-segmenting another axis:

[leeoniya]

here's what a flattened uniform structure would look like that allows i to be logically consistent (with multiple x axis support).

modifying the default y axis or y series would require null or {} placeholders for the skipped default x.

technically, the axes order doesnt matter s long and we can treat the first encountered side: 2 axis as the default x and side: 3 as the default y.

also, axis.side would become a required param, since no default could be assumed just from the position in the array.

there's no such option for series if we want to stay sane and follow the order of data.

{
  data: [
    [1,2,3,4],
    [47,22,13,4]
  ],
  series: [
    null,
    {},
  ],
  axes: [
   null,
   {values: () => {}, side: 3}
  ],
  scales: {
    x: {},
    y: {},
  }
}

there's no need for scales to be an object. we can move to scales being an array as well:

  scales: [
    null,
    {auto: false},
  ]

[thinhdev97]

Have you a sample demo for this? thanks.

[leeoniya]

a sample demo of what?

[thinhdev97]

a sample demo of what?

multiple x-axes like image.
I want to render a time-series chart with 2 lines. But they have different x.

[leeoniya]

chart 2: https://leeoniya.github.io/uPlot/demos/time-periods.html