Aggregate/GroupBy with Distinct to concatenate values instead of counting

Question

I've created a deneb visual where I have a summary aggregation that sums durations by status color. I would like to join/concatenate the statusses belonging to the same color to show as tooltip in the visual.

Given an example dataset of:

Color	Status	Duration
red	Pause	120
red	Offline	30
green	Busy	41
blue	Waiting	32
blue	WrapUp	230
blue	Call	321

I would like to do an aggregate like this:

Color	Status	Duration
red	Pause, Offline	150
green	Busy	41
blue	Waiting, WrapUp, Call	583

There is a join expression (join(array[, separator]) ≥ 5.3) that I thought could help me out here but according to the docs its >5.3. I cannot seem to get that expression to work with my dataset apart from using literal values:

join([1,2,3], ',')

I have the impression I'm looking over something obvious here as this shouldn't be too difficult of a transform. Any ideas?

Keep in mind this is Vega not Vega-Lite.

Answer 1

Here you go.

{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "data": [
    {
      "name": "table",
      "values": [
        {"Color": "red", "Status": "Pause", "Duration": 120},
        {"Color": "red", "Status": "Offline", "Duration": 30},
        {"Color": "green", "Status": "Busy", "Duration": 41},
        {"Color": "blue", "Status": "Waiting", "Duration": 32},
        {"Color": "blue", "Status": "WrapUp", "Duration": 230},
        {"Color": "blue", "Status": "Call", "Duration": 321}
      ],
      "transform": [
        {
          "type": "aggregate",
          "groupby":["Color"],
          "fields": ["Status", "Duration"],
          "ops": ["values", "sum"],
          "as": ["Status", "Duration"]
        },
        {"type": "formula", "as": "Status", "expr": "pluck(datum.Status, 'Status')"}
      ]
    }
  ]
}