نمایش مبدأ برای Extension:Graph/Demo/IndexChart

''From http://vega.github.io/vega-editor/?spec=index_chart''
<graph mode=interactive title="Stock Market">
{
  "version": 2,
  "width": 650,
  "height": 300,
  "padding": "strict",
  "signals": [
    {
      "name": "indexDate",
      "init": {"expr": "time('Jan 1 2005')"},
      "streams": [{
        "type": "mousemove",
        "expr": "clamp(eventX(), 0, eventGroup('root').width)",
        "scale": {"name": "x", "invert": true}
      }]
    },
    {"name": "maxDate", "init": {"expr": "time('Mar 1 2010')"}}
  ],

  "data": [
    {
      "name": "stocks",
      "url": "wikiraw:///Extension:Graph/data/stocks-csv",
      "format": {"type": "csv", "parse": {"price":"number", "date":"date"}}
    },
    {
      "name": "index",
      "source": "stocks",
      "transform": [{
        "type": "filter",
        "test": "month(datum.date) == month(indexDate) && year(datum.date) == year(indexDate)"
      }]
    },
    {
      "name": "indexified_stocks",
      "source": "stocks",
      "transform": [{
        "type": "lookup",
        "on": "index", "onKey": "symbol",
        "keys": ["symbol"], "as": ["index_term"],
        "default": {"price": 0}
      }, {
        "type": "formula",
        "field": "indexed_price",
        "expr": "datum.index_term.price > 0 ? (datum.price - datum.index_term.price)/datum.index_term.price : 0"
      }]
    }
  ],

  "scales": [
    {
      "name": "x",
      "type": "time",
      "domain": {"data": "stocks", "field": "date"},
      "range": "width"
    },
    {
      "name": "y",
      "type": "linear",
      "domain": {"data": "indexified_stocks", "field": "indexed_price"},
      "range": "height",
      "nice": true
    },
    {
      "name": "color", 
      "type": "ordinal", 
      "domain": {"data": "stocks", "field": "symbol"},
      "range": "category10"
    }
  ],
  "axes": [
    {"type": "y", "scale": "y", "grid": true, "layer": "back", "format": "%"}
  ],
  "marks": [
    {
      "type": "group",
      "from": {
        "data": "indexified_stocks",
        "transform": [{"type": "facet", "groupby": ["symbol"]}]
      },
      "marks": [
        {
          "type": "line",
          "properties": {
            "update": {
              "x": {"scale": "x", "field": "date"},
              "y": {"scale": "y", "field": "indexed_price"},
              "stroke": {"scale": "color", "field": "symbol"},
              "strokeWidth": {"value": 2}
            }
          }
        },
        {
          "type": "text",
          "from": {
            "transform": [{"type": "filter", "test": "datum.date == maxDate"}]
          },
          "properties": {
            "update": {
              "x": {"scale": "x", "field": "date", "offset": 2},
              "y": {"scale": "y", "field": "indexed_price"},
              "fill": {"scale": "color", "field": "symbol"},
              "text": {"field": "symbol"},
              "baseline": {"value": "middle"}
            }
          }
        }
      ]
    },
    {
      "type":"rule",
      "properties": {
        "update": {
          "x": {"field": {"group": "x"}},
          "x2": {"field": {"group": "width"}},
          "y": {"scale": "y", "value": 0},
          "stroke": {"value": "black"},
          "strokeWidth": {"value": 1}
        }
      }
    },
    {
      "type":"rule",
      "properties": {
        "update": {
          "x": {"scale": "x", "signal": "indexDate"},
          "y": {"value": 0},
          "y2": {"field": {"group": "height"}},
          "stroke": {"value": "red"}
        }
      }
    },
    {
      "type":"text",
      "properties": {
        "update": {
          "x": {"scale": "x", "signal": "indexDate"},
          "y2": {"field": {"group": "height"}, "offset": 15},
          "align": {"value": "center"},
          "text": {"template": "\u007B{indexDate | time: '%b %Y'}}"},
          "fill": {"value": "red"}
        }
      }
    }
  ]
}
</graph>