Vega Stacked Area 100%

stacked-area-100pct.json

{
  "width": 500,
  "height": 200,
  "padding": "auto",
  "data": [
    {
      "name": "table",
      "values": [
        {"x": 0, "y": 28, "c":0}, {"x": 0, "y": 55, "c":1},
        {"x": 1, "y": 43, "c":0}, {"x": 1, "y": 91, "c":1},
        {"x": 2, "y": 81, "c":0}, {"x": 2, "y": 53, "c":1},
        {"x": 3, "y": 19, "c":0}, {"x": 3, "y": 87, "c":1},
        {"x": 4, "y": 52, "c":0}, {"x": 4, "y": 48, "c":1},
        {"x": 5, "y": 24, "c":0}, {"x": 5, "y": 49, "c":1},
        {"x": 6, "y": 87, "c":0}, {"x": 6, "y": 66, "c":1},
        {"x": 7, "y": 17, "c":0}, {"x": 7, "y": 27, "c":1},
        {"x": 8, "y": 68, "c":0}, {"x": 8, "y": 16, "c":1},
        {"x": 9, "y": 49, "c":0}, {"x": 9, "y": 15, "c":1}
      ]
    },
    {
      "name": "stats",
      "source": "table",
      "transform": [
        {
          "type": "aggregate",
          "groupby": ["x"],
          "summarize": [{"field": "y", "ops": ["sum"]}]
        }
      ]
    }
  ],
  "scales": [
    {
      "name": "x",
      "type": "ordinal",
      "range": "width",
      "points": true,
      "domain": {"data": "table", "field": "x"}
    },
    {
      "name": "y",
      "type": "linear",
      "range": "height",
      "nice": true,
      "domain": [0,1]
    },
    {
      "name": "color",
      "type": "ordinal",
      "range": "category20",
      "domain": {"data": "table", "field": "c"}
    }
  ],
  "axes": [
    {"type": "x", "scale": "x"},
    {"type": "y", "scale": "y", "format": "%"}
  ],
  
  "marks": [
    {
      "type": "group",
      "from": {
        "data": "table",
        "transform": [
          {"type": "lookup", "on": "stats", "onKey": "x", "keys": "x", "as": "sum_y"},
          {"type": "formula", "field": "pcttot", "expr": "datum.y/datum.sum_y.sum_y"},
          {"type": "stack", "groupby": ["x"], "sortby": ["c"], "field": "pcttot"},
          {"type": "facet", "groupby": ["c"]}
        ]
      },
      "marks": [
        {
          "type": "area",
          "properties": {
            "enter": {
              "interpolate": {"value": "monotone"},
              "x": {"scale": "x", "field": "x"},
              "y": {"scale": "y", "field": "layout_start"},
              "y2": {"scale": "y", "field": "layout_end"},
              "fill": {"scale": "color", "field": "c"}
            }
          }
        }
      ]
    }
  ]
}