{
    "mark": {
        "point": true,
        "type": "line"
    },
    "data": {
        "values": [
            {
                "x": 1,
                "y": 10
            },
            {
                "x": 2,
                "y": 30
            },
            {
                "x": 3,
                "y": null
            },
            {
                "x": 4,
                "y": 15
            },
            {
                "x": 5,
                "y": null
            },
            {
                "x": 6,
                "y": 40
            },
            {
                "x": 7,
                "y": 20
            }
        ]
    },
    "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
    "encoding": {
        "x": {
            "field": "x",
            "type": "quantitative"
        },
        "y": {
            "field": "y",
            "type": "quantitative"
        }
    },
    "description": "Line chart with markers and invalid values."
}