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  "width": 900,
  "height": 560,
  "padding": {"top": 25, "left": 0, "right": 0, "bottom": 0},
  "autosize": "none",

  "signals": [
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      "name": "scale", "value": 1200,
      "bind": {"input": "range", "min": 500, "max": 3000}
    },
    {
      "name": "translateX", "value": 450,
      "bind": {"input": "range", "min": -500, "max": 1200}
    },
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      "name": "translateY", "value": 260,
      "bind": {"input": "range", "min": -300, "max": 700}
    },
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      "name": "shape", "value": "line",
      "bind": {"input": "radio", "options": ["line", "curve"]}
    },
    {
      "name": "hover",
      "value": null,
      "on": [
        {"events": "@cell:pointerover", "update": "datum"},
        {"events": "@cell:pointerout", "update": "null"}
      ]
    },
    {
      "name": "title",
      "value": "U.S. Airports, 2008",
      "update": "hover ? hover.name + ' (' + hover.iata + ')' : 'U.S. Airports, 2008'"
    },
    {
      "name": "cell_stroke",
      "value": null,
      "on": [
        {"events": "dblclick", "update": "cell_stroke ? null : 'brown'"},
        {"events": "pointerdown!", "update": "cell_stroke"}
      ]
    }
  ],

  "data": [
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      "name": "states",
      "url": "data/us-10m.json",
      "format": {"type": "topojson", "feature": "states"},
      "transform": [
        {
          "type": "geopath",
          "projection": "projection"
        }
      ]
    },
    {
      "name": "traffic",
      "url": "data/flights-airport.csv",
      "format": {"type": "csv", "parse": "auto"},
      "transform": [
        {
          "type": "aggregate",
          "groupby": ["origin"],
          "fields": ["count"], "ops": ["sum"], "as": ["flights"]
        }
      ]
    },
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      "name": "airports",
      "url": "data/airports.csv",
      "format": {"type": "csv", "parse": "auto"},
      "transform": [
        {
          "type": "lookup",
          "from": "traffic", "key": "origin",
          "fields": ["iata"], "as": ["traffic"]
        },
        {
          "type": "filter",
          "expr": "datum.traffic != null"
        },
        {
          "type": "geopoint",
          "projection": "projection",
          "fields": ["longitude", "latitude"]
        },
        {
          "type": "filter",
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        },
        {
          "type": "voronoi", "x": "x", "y": "y"
        },
        {
          "type": "collect", "sort": {
            "field": "traffic.flights",
            "order": "descending"
          }
        }
      ]
    },
    {
      "name": "routes",
      "url": "data/flights-airport.csv",
      "format": {"type": "csv", "parse": "auto"},
      "transform": [
        {
          "type": "filter",
          "expr": "hover && hover.iata == datum.origin"
        },
        {
          "type": "lookup",
          "from": "airports", "key": "iata",
          "fields": ["origin", "destination"], "as": ["source", "target"]
        },
        {
          "type": "filter",
          "expr": "datum.source && datum.target"
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          "shape": {"signal": "shape"}
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  "projections": [
    {
      "name": "projection",
      "type": "albersUsa",
      "scale": {"signal": "scale"},
      "translate": [{"signal": "translateX"}, {"signal": "translateY"}]
    }
  ],

  "scales": [
    {
      "name": "size",
      "type": "linear",
      "domain": {"data": "traffic", "field": "flights"},
      "range": [16, 1000]
    }
  ],

  "marks": [
    {
      "type": "path",
      "from": {"data": "states"},
      "encode": {
        "enter": {
          "fill": {"value": "#dedede"},
          "stroke": {"value": "white"}
        },
        "update": {
          "path": {"field": "path"}
        }
      }
    },
    {
      "type": "symbol",
      "from": {"data": "airports"},
      "encode": {
        "enter": {
          "size": {"scale": "size", "field": "traffic.flights"},
          "fill": {"value": "steelblue"},
          "fillOpacity": {"value": 0.8},
          "stroke": {"value": "white"},
          "strokeWidth": {"value": 1.5}
        },
        "update": {
          "x": {"field": "x"},
          "y": {"field": "y"}
        }
      }
    },
    {
      "type": "path",
      "name": "cell",
      "from": {"data": "airports"},
      "encode": {
        "enter": {
          "fill": {"value": "transparent"},
          "strokeWidth": {"value": 0.35}
        },
        "update": {
          "path": {"field": "path"},
          "stroke": {"signal": "cell_stroke"}
        }
      }
    },
    {
      "type": "path",
      "interactive": false,
      "from": {"data": "routes"},
      "encode": {
        "enter": {
          "path": {"field": "path"},
          "stroke": {"value": "black"},
          "strokeOpacity": {"value": 0.35}
        }
      }
    },
    {
      "type": "text",
      "interactive": false,
      "encode": {
        "enter": {
          "x": {"value": 895},
          "y": {"value": 0},
          "fill": {"value": "black"},
          "fontSize": {"value": 20},
          "align": {"value": "right"}
        },
        "update": {
          "text": {"signal": "title"}
        }
      }
    }
  ]
}
