Airport Connections Example

Vega Airport Connections Example and the corresponding tutorial.

Vega example

NetPanorama example

Vega specification

	{ "$schema": "https://vega.github.io/schema/vega/v5.json", "description": "Interactive map of U.S. airport connections in 2008.", "width": 900, "height": 560, "padding": {"top": 25, "left": 0, "right": 0, "bottom": 0}, "autosize": "none",
Signals required for interactivity	"signals": [ { "name": "scale", "value": 1200, "bind": {"input": "range", "min": 500, "max": 3000} }, { "name": "translateX", "value": 450, "bind": {"input": "range", "min": -500, "max": 1200} }, { "name": "translateY", "value": 260, "bind": {"input": "range", "min": -300, "max": 700} }, { "name": "shape", "value": "line", "bind": {"input": "radio", "options": ["line", "curve"]} }, { "name": "hover", "value": null, "on": [ {"events": "@cell:mouseover", "update": "datum"}, {"events": "@cell:mouseout", "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": "mousedown!", "update": "cell_stroke"} ] } ],
	"data": [
load data for background map	{ "name": "states", "url": "https://vega.github.io/vega/data/us-10m.json", "format": {"type": "topojson", "feature": "states"}, "transform": [ { "type": "geopath", "projection": "projection" } ] },
load flight data, and apply transform to calculate total number of flights per airport	{ "name": "traffic", "url": "https://vega.github.io/vega/data/flights-airport.csv", "format": {"type": "csv", "parse": "auto"}, "transform": [ { "type": "aggregate", "groupby": ["origin"], "fields": ["count"], "ops": ["sum"], "as": ["flights"] } ] },
Load airport data and transform: join with flight counts, remove airports with no flights, project lat/lon, remove airports with unknown location, compute Voroni cell around each airport, and sort by flight count	{ "name": "airports", "url": "https://vega.github.io/vega/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", "expr": "datum.x != null && datum.y != null" }, { "type": "voronoi", "x": "x", "y": "y" }, { "type": "collect", "sort": { "field": "traffic.flights", "order": "descending" } } ] },
load flight data, and transform to: remove all rows except for those whose origin is the hovered-over airport, then construct linkpath	{ "name": "routes", "url": "https://vega.github.io/vega/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" }, { "type": "linkpath", "shape": {"signal": "shape"} } ] } ],
Projections and scales	"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": [
draw shapes for states	{ "type": "path", "from": {"data": "states"}, "encode": { "enter": { "fill": {"value": "#dedede"}, "stroke": {"value": "white"} }, "update": { "path": {"field": "path"} } } },
draw a circle for each airport	{ "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"} } } },
draw an invisible Voronoi cell around each airport to act as a hover target	{ "type": "path", "name": "cell", "from": {"data": "airports"}, "encode": { "enter": { "fill": {"value": "transparent"}, "strokeWidth": {"value": 0.35} }, "update": { "path": {"field": "path"}, "stroke": {"signal": "cell_stroke"} } } },
draw a path for each flight route from the hovered node	{ "type": "path", "interactive": false, "from": {"data": "routes"}, "encode": { "enter": { "path": {"field": "path"}, "stroke": {"value": "black"}, "strokeOpacity": {"value": 0.35} } } },
display the name of the hovered airport	{ "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"} } } } ] }

NetPanorama specification

	{
Define paramaters: my_selection will be directly updated by interactions, and then neighbours will be auto-updated to include its neighbours.	"parameters": [ { "name": "my_selection", "action": "replace", "network": "network", "type": "selection" }, { "name": "neighbours", "source": "my_selection", "transform": [ { "type": "neighbours", "direction": "both" } ] } ],
Load data...	"data": [ { "name": "links", "url": "https://vega.github.io/vega/data/flights-airport.csv", "format": {"type": "csv", "parse": "auto"} }, { "name": "nodes", "url": "https://vega.github.io/vega/data/airports.csv", "format": {"type": "csv","parse": "auto"}, "transform": [ {"type": "calculate", "calculate": "datum.iata", "as": "id"} ] } ],
...and assemble into a network. Then remove nodes with no connections, and calculate total flight count for each airport.	"networks": [ { "name": "network", "nodes": "nodes", "links": "links", "directed": true, "source_node": [ "iata", "origin" ], "target_node": [ "iata", "destination" ], "transform": [ {"type": "removeIsolated"}, {"type": "connectivityBasedAttribute", "as": "flights", "attributeSelector": "link.count", "operation": "sum"} ] } ],
Define a scale to set the node sizes.	"scales": [ { "name": "size", "type": "linear", "domain": [0, 1000000], "range": [16, 1000] } ],
Specify which basemap to use, and which geographic region to show.	"maps": [ { "name": "my_map", "tiles": "Stamen_TerrainBackground", "zoomLevel": 4, "center": [40, -87.3] } ],
Construct a layout that positions nodes correctly relative to the basemap.	"layouts": [ { "name": "map-layout", "network": "network", "map": "my_map", "lat": { "field": "latitude" }, "lng": { "field": "longitude" } } ],
/	"vis": [
Render links to neighbours of the selected node.	{ "entries": "network.links", "ifInSelection": "neighbours.links", "layout": "map-layout", "mark": { "type": "linkpath", "start": "source", "end": "target", "strokeWidth": 1, "stroke": "black" } },
Render nodes.	{ "entries": "network.nodes", "layout": "map-layout", "mark": { "type": "circle", "area": { "field": "data.flights", "scale": "size" }, "fill": "steelblue", "fillOpacity": 0.8, "stroke": "white" },
On mouseover, update the selected node.	"actions": [ { "interaction": "select", "using": "cursor", "event": "mouseover", "action": "replace", "selection": "my_selection" } ]
	},
Display name and IATA code for selected node.	{ "mark": { "type": "text", "x": 20, "y": 40, "fontSize": 30, "text": {"expression": "(params.my_selection.nodes.length > 0) ? (params.my_selection.nodes[0].name + ' (' + params.my_selection.nodes[0].iata + ')' ) : '' "} } },
Display the basemap.	{ "mark":{ "type": "map", "map": "my_map" } } ] }