joinAggregate2.vl

{
    "transform": [
        {
            "filter": "datum.IMDB_Rating != null"
        },
        {
            "joinaggregate": [
                {
                    "op": "mean",
                    "as": "AverageRating",
                    "field": "IMDB_Rating"
                }
            ]
        },
        {
            "filter": "(datum.IMDB_Rating - datum.AverageRating) > 2.5"
        }
    ],
    "mark": "bar",
    "data": {
        "url": "https://vega.github.io/vega-lite/data/movies.json"
    },
    "$schema": "https://vega.github.io/schema/vega-lite/v3.json",
    "encoding": {
        "x": {
            "field": "IMDB_Rating",
            "type": "quantitative",
            "axis": {
                "title": "IMDB Rating"
            }
        },
        "y": {
            "field": "Title",
            "sort": {
                "encoding": "x",
                "order": "descending"
            },
            "type": "nominal",
            "axis": {
                "title": ""
            }
        }
    }
}