{
  "$schema": "https://vega.github.io/schema/vega/v5.json",
  "description": "An interactive visualization of connections among major U.S. airports in 2008. Based on a U.S. airports example by Mike Bostock.",
  "background": "white",
  "padding": 5,
  "width": 900,
  "height": 500,
  "data": [
    {"name": "org_store"},
    {
      "name": "source_0",
      "url": "data/us-10m.json",
      "format": {"type": "topojson", "feature": "states"}
    },
    {
      "name": "source_1",
      "url": "data/flights-airport.csv",
      "format": {"type": "csv"}
    },
    {"name": "source_2", "url": "data/airports.csv", "format": {"type": "csv"}},
    {
      "name": "data_0",
      "source": "source_1",
      "transform": [
        {
          "type": "filter",
          "expr": "length(data(\"org_store\")) && vlSelectionTest(\"org_store\", datum)"
        },
        {
          "type": "lookup",
          "from": "source_2",
          "key": "iata",
          "fields": ["origin"],
          "values": ["latitude", "longitude"]
        },
        {
          "type": "lookup",
          "from": "source_2",
          "key": "iata",
          "fields": ["destination"],
          "values": ["latitude", "longitude"],
          "as": ["lat2", "lon2"]
        },
        {
          "type": "geojson",
          "fields": ["longitude", "latitude"],
          "signal": "layer_1_geojson_0"
        },
        {
          "type": "geojson",
          "fields": ["lon2", "lat2"],
          "signal": "layer_1_geojson_1"
        },
        {
          "type": "geopoint",
          "projection": "projection",
          "fields": ["longitude", "latitude"],
          "as": ["layer_1_x", "layer_1_y"]
        },
        {
          "type": "geopoint",
          "projection": "projection",
          "fields": ["lon2", "lat2"],
          "as": ["layer_1_x2", "layer_1_y2"]
        }
      ]
    },
    {
      "name": "data_1",
      "source": "source_1",
      "transform": [
        {
          "type": "aggregate",
          "groupby": ["origin"],
          "ops": ["count"],
          "fields": [null],
          "as": ["routes"]
        },
        {
          "type": "lookup",
          "from": "source_2",
          "key": "iata",
          "fields": ["origin"],
          "values": ["state", "latitude", "longitude"]
        },
        {
          "type": "filter",
          "expr": "datum.state !== 'PR' && datum.state !== 'VI'"
        },
        {
          "type": "geojson",
          "fields": ["longitude", "latitude"],
          "signal": "layer_2_geojson_0"
        },
        {
          "type": "geopoint",
          "projection": "projection",
          "fields": ["longitude", "latitude"],
          "as": ["layer_2_x", "layer_2_y"]
        },
        {
          "type": "filter",
          "expr": "isValid(datum[\"routes\"]) && isFinite(+datum[\"routes\"])"
        }
      ]
    }
  ],
  "projections": [
    {
      "name": "projection",
      "size": {"signal": "[width, height]"},
      "fit": {
        "signal": "[data('source_0'), layer_1_geojson_0, layer_1_geojson_1, layer_2_geojson_0]"
      },
      "type": "albersUsa"
    }
  ],
  "signals": [
    {
      "name": "unit",
      "value": {},
      "on": [
        {"events": "mousemove", "update": "isTuple(group()) ? group() : unit"}
      ]
    },
    {
      "name": "org",
      "update": "vlSelectionResolve(\"org_store\", \"union\", true, true)"
    },
    {
      "name": "org_tuple",
      "on": [
        {
          "events": [
            {
              "source": "scope",
              "type": "mouseover",
              "markname": "layer_2_voronoi"
            }
          ],
          "update": "datum && item().mark.marktype !== 'group' ? {unit: \"layer_2\", fields: org_tuple_fields, values: [(item().isVoronoi ? datum.datum : datum)[\"origin\"]]} : null",
          "force": true
        },
        {"events": [{"source": "view", "type": "dblclick"}], "update": "null"}
      ]
    },
    {"name": "org_tuple_fields", "value": [{"type": "E", "field": "origin"}]},
    {
      "name": "org_toggle",
      "value": false,
      "on": [
        {
          "events": [
            {
              "source": "scope",
              "type": "mouseover",
              "markname": "layer_2_voronoi"
            }
          ],
          "update": "event.shiftKey"
        },
        {"events": [{"source": "view", "type": "dblclick"}], "update": "false"}
      ]
    },
    {
      "name": "org_modify",
      "on": [
        {
          "events": {"signal": "org_tuple"},
          "update": "modify(\"org_store\", org_toggle ? null : org_tuple, org_toggle ? null : true, org_toggle ? org_tuple : null)"
        }
      ]
    }
  ],
  "marks": [
    {
      "name": "layer_0_marks",
      "type": "shape",
      "style": ["geoshape"],
      "interactive": false,
      "from": {"data": "source_0"},
      "encode": {
        "update": {
          "fill": {"value": "#ddd"},
          "stroke": {"value": "#fff"},
          "strokeWidth": {"value": 1},
          "ariaRoleDescription": {"value": "geoshape"}
        }
      },
      "transform": [{"type": "geoshape", "projection": "projection"}]
    },
    {
      "name": "layer_1_marks",
      "type": "rule",
      "style": ["rule"],
      "interactive": false,
      "from": {"data": "data_0"},
      "encode": {
        "update": {
          "opacity": {"value": 0.35},
          "stroke": {"value": "#000"},
          "description": {
            "signal": "\"longitude: \" + (format(datum[\"longitude\"], \"\")) + \"; lon2: \" + (format(datum[\"lon2\"], \"\")) + \"; latitude: \" + (format(datum[\"latitude\"], \"\")) + \"; lat2: \" + (format(datum[\"lat2\"], \"\"))"
          },
          "x": {"field": "layer_1_x"},
          "x2": {"field": "layer_1_x2"},
          "y": {"field": "layer_1_y"},
          "y2": {"field": "layer_1_y2"}
        }
      }
    },
    {
      "name": "layer_2_marks",
      "type": "symbol",
      "style": ["circle"],
      "sort": {"field": ["datum[\"routes\"]"], "order": ["descending"]},
      "interactive": true,
      "from": {"data": "data_1"},
      "encode": {
        "update": {
          "opacity": {"value": 0.7},
          "fill": {"value": "#4c78a8"},
          "ariaRoleDescription": {"value": "circle"},
          "description": {
            "signal": "\"longitude: \" + (format(datum[\"longitude\"], \"\")) + \"; latitude: \" + (format(datum[\"latitude\"], \"\")) + \"; routes: \" + (format(datum[\"routes\"], \"\"))"
          },
          "x": {"field": "layer_2_x"},
          "y": {"field": "layer_2_y"},
          "size": {"scale": "size", "field": "routes"},
          "shape": {"value": "circle"}
        }
      }
    },
    {
      "name": "layer_2_voronoi",
      "type": "path",
      "interactive": true,
      "from": {"data": "layer_2_marks"},
      "encode": {
        "update": {
          "fill": {"value": "transparent"},
          "strokeWidth": {"value": 0.35},
          "stroke": {"value": "transparent"},
          "isVoronoi": {"value": true}
        }
      },
      "transform": [
        {
          "type": "voronoi",
          "x": {"expr": "datum.datum.x || 0"},
          "y": {"expr": "datum.datum.y || 0"},
          "size": [{"signal": "width"}, {"signal": "height"}]
        }
      ]
    }
  ],
  "scales": [
    {
      "name": "size",
      "type": "linear",
      "domain": {"data": "data_1", "field": "routes"},
      "range": [0, 1000],
      "zero": true
    }
  ]
}