{
    "transform": [
        {
            "as": "YearOfManufacture",
            "calculate": "year(datum.Year)"
        },
        {
            "filter": "datum.YearOfManufacture == 1970"
        }
    ],
    "mark": {
        "shape": "wedge",
        "type": "point",
        "filled": false
    },
    "data": {
        "url": "https://vega.github.io/vega-lite/data/cars.json"
    },
    "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
    "encoding": {
        "opacity": {
            "value": 0.6
        },
        "x": {
            "field": "Horsepower",
            "type": "quantitative"
        },
        "y": {
            "field": "Miles_per_Gallon",
            "type": "quantitative"
        }
    },
    "description": "wedge-unfilled"
}