transform1.vl

{
    "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
    "data": {
        "format": {
            "parse": {
                "NOX": "number"
            }
        },
        "url": "https://gicentre.github.io/data/putneyAirQuality2018.csv"
    },
    "description": "Cumulative Frequency Distribution",
    "encoding": {
        "x": {
            "field": "NOX",
            "title": "NOX concentration (μg/㎥)",
            "type": "quantitative"
        },
        "y": {
            "field": "cumulativeCount",
            "type": "quantitative"
        }
    },
    "mark": {
        "fill": {
            "gradient": "linear",
            "stops": [
                {
                    "color": "white",
                    "offset": 0
                },
                {
                    "color": "black",
                    "offset": 1
                }
            ],
            "x1": 0,
            "x2": 1,
            "y1": 1,
            "y2": 1
        },
        "fillOpacity": 0.5,
        "stroke": {
            "gradient": "linear",
            "stops": [
                {
                    "color": "orange",
                    "offset": 0
                },
                {
                    "color": "green",
                    "offset": 0.5
                },
                {
                    "color": "purple",
                    "offset": 1
                }
            ]
        },
        "strokeDash": [
            10,
            6,
            6,
            6
        ],
        "strokeDashOffset": 5,
        "strokeOpacity": 0.8,
        "strokeWidth": 2,
        "type": "area"
    },
    "transform": [
        {
            "sort": [
                {
                    "field": "NOX",
                    "order": "ascending"
                }
            ],
            "window": [
                {
                    "as": "cumulativeCount",
                    "op": "count"
                }
            ]
        }
    ],
    "width": 500
}