stack1.vl

{
    "transform": [
        {
            "groupby": [
                "Origin",
                "Cylinders"
            ],
            "aggregate": [
                {
                    "op": "count",
                    "as": "count_*"
                }
            ]
        },
        {
            "groupby": [],
            "as": [
                "stack_count_Origin1",
                "stack_count_Origin2"
            ],
            "offset": "normalize",
            "sort": [
                {
                    "field": "Origin",
                    "order": "ascending"
                }
            ],
            "stack": "count_*"
        },
        {
            "window": [
                {
                    "op": "min",
                    "as": "x",
                    "field": "stack_count_Origin1"
                },
                {
                    "op": "max",
                    "as": "x2",
                    "field": "stack_count_Origin2"
                }
            ],
            "groupby": [
                "Origin"
            ],
            "frame": [
                null,
                null
            ]
        },
        {
            "groupby": [
                "Origin"
            ],
            "as": [
                "y",
                "y2"
            ],
            "offset": "normalize",
            "sort": [
                {
                    "field": "Cylinders",
                    "order": "ascending"
                }
            ],
            "stack": "count_*"
        }
    ],
    "mark": "rect",
    "data": {
        "url": "https://vega.github.io/vega-lite/data/cars.json"
    },
    "$schema": "https://vega.github.io/schema/vega-lite/v3.json",
    "encoding": {
        "x2": {
            "field": "x2"
        },
        "color": {
            "field": "Origin",
            "type": "nominal"
        },
        "opacity": {
            "field": "Cylinders",
            "type": "quantitative",
            "legend": null
        },
        "tooltip": [
            {
                "field": "Origin",
                "type": "nominal"
            },
            {
                "field": "Cylinders",
                "type": "quantitative"
            }
        ],
        "x": {
            "field": "x",
            "type": "quantitative",
            "axis": null
        },
        "y2": {
            "field": "y2"
        },
        "y": {
            "field": "y",
            "type": "quantitative",
            "axis": null
        }
    }
}