advanced7.vl

{
    "transform": [
        {
            "from": {
                "data": {
                    "url": "https://vega.github.io/vega-lite/data/lookup_people.csv"
                },
                "key": "name",
                "fields": [
                    "age",
                    "height"
                ]
            },
            "lookup": "person"
        }
    ],
    "mark": "bar",
    "data": {
        "url": "https://vega.github.io/vega-lite/data/lookup_groups.csv"
    },
    "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
    "encoding": {
        "x": {
            "field": "group",
            "type": "ordinal"
        },
        "y": {
            "field": "age",
            "aggregate": "mean",
            "type": "quantitative"
        }
    },
    "description": "Using the lookup transform to combine data"
}