Feature request: default colours for groups

[ntthung]

In the vgg-multi-line example, the groupBy operation was carried out on the colours. In a real life case, users are more likely to group by some sort of ID. The user will then need to write a method to map from IDs to colours. It would be nice to set default colours for groups.

[luucvanderzee]

a method to map from IDs to colours.

So... a (categorical) color scale?

[bianchi-dy]

Hi @ntthung, would you be referring to categorical color scales here? We do have support for those found in d3: Categorical Color Scales, but please elaborate if they're not exactly what you had in mind.

These can be specified the same way you currently specify other color scales like reds:

{ type: 'category10' }

[ntthung]

I realized that I can do :stroke="{ val: row.id, scale: { type: 'category10', domain: 'id' } }". So this is not really a feature request anymore.

But let me explained my thought process. I was looking at this example in vgg-multi-line

<vgg-graphic
  :width="200"
  :height="250"
  :data="{ 
    year: [
      2000, 2005, 2010, 2015,
      2000, 2005, 2010, 2015
    ],
    population: [
      100, 110, 130, 180,
      200, 310, 430, 480
    ],
    color: [
      '#c66366', '#c66366', '#c66366',
      '#c66366', '#008080', '#008080',
      '#008080', '#008080'
    ]
  }">

  <vgg-section
    :x1="25"
    :x2="175"
    :y1="25"
    :y2="225"
    scale-x="year"
    scale-y="population"
    :axes="{
      left: {'tick-count': 4, 'w': 30},
      bottom: {'tick-count': 4}
    }"
  >
    <vgg-data :transform="{ groupBy: 'color' }">
    
      <vgg-map v-slot="{ row }">

        <vgg-multi-line
          :x="row.grouped.year"
          :y="row.grouped.population"
          :stroke="row.color"
        />

      </vgg-map>

    </vgg-data>

  </vgg-section>

</vgg-graphic>

And then I replaced color with id and it didn't work. Of course it didn't work, because IDs are not colours. But I was just thinking of colour as a normal attribute. This is probably because I came from a ggplot background.

So perhaps only the documentation needs to be clarified.