{
    "height": 500,
    "config": {
        "view": {
            "stroke": null
        }
    },
    "width": 900,
    "$schema": "https://vega.github.io/schema/vega-lite/v4.json",
    "projection": {
        "type": "albersUsa"
    },
    "layer": [
        {
            "mark": {
                "stroke": "#fff",
                "fill": "#ddd",
                "type": "geoshape"
            },
            "data": {
                "url": "https://vega.github.io/vega-lite/data/us-10m.json",
                "format": {
                    "feature": "states",
                    "type": "topojson"
                }
            }
        },
        {
            "transform": [
                {
                    "filter": {
                        "selection": "mySelection"
                    }
                },
                {
                    "as": "o",
                    "from": {
                        "data": {
                            "url": "https://vega.github.io/vega-lite/data/airports.csv"
                        },
                        "key": "iata"
                    },
                    "lookup": "origin"
                },
                {
                    "as": "d",
                    "from": {
                        "data": {
                            "url": "https://vega.github.io/vega-lite/data/airports.csv"
                        },
                        "key": "iata"
                    },
                    "lookup": "destination"
                }
            ],
            "mark": {
                "color": "black",
                "opacity": 0.35,
                "type": "rule"
            },
            "data": {
                "url": "https://vega.github.io/vega-lite/data/flights-airport.csv"
            },
            "encoding": {
                "latitude": {
                    "field": "o.latitude",
                    "type": "quantitative"
                },
                "latitude2": {
                    "field": "d.latitude"
                },
                "longitude": {
                    "field": "o.longitude",
                    "type": "quantitative"
                },
                "longitude2": {
                    "field": "d.longitude"
                }
            }
        },
        {
            "transform": [
                {
                    "groupby": [
                        "origin"
                    ],
                    "aggregate": [
                        {
                            "op": "count",
                            "as": "routes"
                        }
                    ]
                },
                {
                    "from": {
                        "data": {
                            "url": "https://vega.github.io/vega-lite/data/airports.csv"
                        },
                        "key": "iata",
                        "fields": [
                            "name",
                            "state",
                            "latitude",
                            "longitude"
                        ]
                    },
                    "lookup": "origin"
                },
                {
                    "filter": "datum.state !== 'PR' && datum.state !== 'VI'"
                }
            ],
            "mark": "circle",
            "data": {
                "url": "https://vega.github.io/vega-lite/data/flights-airport.csv"
            },
            "selection": {
                "mySelection": {
                    "nearest": true,
                    "empty": "none",
                    "type": "single",
                    "on": "mouseover",
                    "fields": [
                        "origin"
                    ]
                }
            },
            "encoding": {
                "size": {
                    "field": "routes",
                    "scale": {
                        "range": [
                            0,
                            1000
                        ]
                    },
                    "type": "quantitative",
                    "legend": null
                },
                "latitude": {
                    "field": "latitude",
                    "type": "quantitative"
                },
                "tooltip": {
                    "field": "name",
                    "type": "nominal"
                },
                "longitude": {
                    "field": "longitude",
                    "type": "quantitative"
                },
                "order": {
                    "field": "routes",
                    "sort": "descending",
                    "type": "quantitative"
                }
            }
        }
    ],
    "description": "One dot per airport in the US overlayed on geoshape"
}