Area Chart Example

{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "A basic area chart example.",
  "width": 500,
  "height": 200,
  "padding": 5,

  "signals": [
    {
      "name": "interpolate",
      "value": "monotone",
      "bind": {
        "input": "select",
        "options": [
          "basis",
          "cardinal",
          "catmull-rom",
          "linear",
          "monotone",
          "natural",
          "step",
          "step-after",
          "step-before"
        ]
      }
    }
  ],

  "data": [
    {
      "name": "table",
      "values": [
        {"u": 1,  "v": 28}, {"u": 2,  "v": 55},
        {"u": 3,  "v": 43}, {"u": 4,  "v": 91},
        {"u": 5,  "v": 81}, {"u": 6,  "v": 53},
        {"u": 7,  "v": 19}, {"u": 8,  "v": 87},
        {"u": 9,  "v": 52}, {"u": 10, "v": 48},
        {"u": 11, "v": 24}, {"u": 12, "v": 49},
        {"u": 13, "v": 87}, {"u": 14, "v": 66},
        {"u": 15, "v": 17}, {"u": 16, "v": 27},
        {"u": 17, "v": 68}, {"u": 18, "v": 16},
        {"u": 19, "v": 49}, {"u": 20, "v": 15}
      ]
    }
  ],

  "scales": [
    {
      "name": "xscale",
      "type": "linear",
      "range": "width",
      "zero": false,
      "domain": {"data": "table", "field": "u"}
    },
    {
      "name": "yscale",
      "type": "linear",
      "range": "height",
      "nice": true,
      "zero": true,
      "domain": {"data": "table", "field": "v"}
    }
  ],

  "axes": [
    {"orient": "bottom", "scale": "xscale", "tickCount": 20},
    {"orient": "left", "scale": "yscale"}
  ],

  "marks": [
    {
      "type": "area",
      "from": {"data": "table"},
      "encode": {
        "enter": {
          "x": {"scale": "xscale", "field": "u"},
          "y": {"scale": "yscale", "field": "v"},
          "y2": {"scale": "yscale", "value": 0},
          "fill": {"value": "steelblue"}
        },
        "update": {
          "interpolate": {"signal": "interpolate"},
          "fillOpacity": {"value": 1}
        },
        "hover": {
          "fillOpacity": {"value": 0.5}
        }
      }
    }
  ]
}