Vega: extract two different properties from source data

Question

I'm trying to use Vega to visualise the results of a query from elasticsearch.

The actual response from elasticsearch will look like what's in the first data entry below, named "es_response". I need to split that response data into two different data, which I named histogram_data and rule_data

I tried using format: { property: "..." } to extract the values in each subdata (as shown below), but it's not allowed by the language.

I also tried using various combinations of Transforms to separate that data, but couldn't get any good result.

What's the best way to do that?

Link to the original vega-lite source

  "data": [
    {
      "name": "es_response",
      "values": {
        "aggregations": {
          "histogram": [
            {"a": 30, "b": 28},
            {"a": 40, "b": 55},
            {"a": 50, "b": 43},
            {"a": 60, "b": 91},
            {"a": 70, "b": 81},
            {"a": 80, "b": 53},
            {"a": 90, "b": 19},
            {"a": 100, "b": 87},
            {"a": 110, "b": 52}
          ],
          "percentiles": {
            "values": [
              {
                "key": 50,
                "value": 100
              }
            ]
          }
        }
      }
    },
    {
      "name": "histogram_data",
      "source": "es_response",
       
      /*
       * This doesn't work, but I really wish it did
       */
      "format": { "property": "aggregations.histogram"}
    },
    {
      "name": "percentile_data",
      "source": "es_response",
 
      /*
       * Same here
       */
      "format": { "property": "aggregations.percentiles.values"}
    }
  ]

Answer 1

This is a bug in Vega-Lite right now which is tracked at https://github.com/vega/vega-lite/issues/5034.