axisDateCondition1.vl

{
    "mark": {
        "borders": {},
        "extent": "iqr",
        "interpolate": "monotone",
        "type": "errorband"
    },
    "data": {
        "url": "https://vega.github.io/vega-lite/data/cars.json"
    },
    "width": 600,
    "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
    "encoding": {
        "x": {
            "field": "Year",
            "timeUnit": "year",
            "type": "temporal",
            "axis": {
                "gridWidth": {
                    "value": 1,
                    "condition": {
                        "value": 4,
                        "test": {
                            "equal": {
                                "date": 1,
                                "month": "Jan"
                            },
                            "field": "value",
                            "timeUnit": "monthdate"
                        }
                    }
                }
            }
        },
        "y": {
            "field": "Miles_per_Gallon",
            "scale": {
                "zero": false
            },
            "type": "quantitative"
        }
    }
}