30:T94e,md`# Census: Shapefile Demographics A general tool to generate census demographic data from arbitrary shapefiles. This tool utilizes block-level census data from the 2010 census to approximate demographics of any polygon. It is inspired by a [tweet](https://twitter.com/jkeefe/status/1269381497456394243) by John Keefe looking at demographic data by NYPD police precinct and some of my previous work reporting COVID demographics. To get started, upload a Shapefile ZIP archive below or select an example. Once it is done processing, you can view demographic information by clicking on orange regions on the map below. You can download the results by using the buttons below the map. **NOTE:** It may take a while (up to a few minutes) to process after selecting your files. Please be patient (results are cached so subsequent runs of the same files will be speedy). I recommend not changing windows or hitting any buttons while it's processing. If an "Infinite Loop" warning comes up, hit "Dismiss."

Technical details

Blocks are the lowest unit the census offers. When a block is only partially overlaps a polygon, the polygon inherits a fraction of the block's demographic information proportional to the overlapping area.

This tool utilizes the Census's TIGERweb REST services to first grab tract polygons, and then grab block polygons for cases where overlap occur (using a convex hull over the request geometry to fetch as few blocks as possible). The Census's CitySDK is used to grab demographic data. All calls are memoized using local storage to prevent spamming the Census API and speed up future executions.

Have a census key? If not, go here to register one. Set localStorage['census-api-key'] = <YOUR_API_KEY> in a new code cell to enjoy unrestricted API limits. (A census API key gives you unrestricted access to the Census API and is useful if you're in a shared workspace; it should be pretty hard to hit API limits otherwise).

TODO:

Performance improvements (get TIGER sub-tract geo with property queries)
Investigate using a service worker script
ACS block group data for more recent estimates
GitHub repo to share code

---`31:Tb7d,viewof resultData = { const bar = progress({interval: 50, invalidation}); yield bar; if (shapeDataEmpty) { bar.resolve(null); return; } // Run all code await bar.progress(0, 'Calculating convex hull'); const hull = convexHull(shapeData); // Start with tracts await bar.progress(0.1, 'Fetching census tracts from TIGERweb'); const tigerGeoTracts = await tigerPoly(hull, TRACT); await bar.progress(0.2, 'Retrieving census tracts from CitySDK'); const statesCounties = getStatesCounties(tigerGeoTracts); const censusDataTracts = await retrieveCensusData(statesCounties, 'tract'); await bar.progress(0.3, 'Blending census tracts together'); let [mixedShapeData, stragglerTracts] = await mixCensusIntoShapefile(shapeData, tigerGeoTracts, censusDataTracts, [['state', 'STATE'], ['county', 'COUNTY'], ['tract', 'TRACT']], false, true); const stragglerTractStrings = stragglerTracts.map(x => `${x.properties.STATE}-${x.properties.COUNTY}-${x.properties.TRACT}`); // Get block groups from stragglers await bar.progress(0.4, 'Fetching census block groups that overlapped from TIGERweb'); const tigerGeoBlockGroupsAll = await tigerPoly(hull, BLOCK_GROUP); const tigerGeoBlockGroups = turf.featureCollection(tigerGeoBlockGroupsAll.features.filter(x => stragglerTractStrings.includes(`${x.properties.STATE}-${x.properties.COUNTY}-${x.properties.TRACT}`))); await bar.progress(0.5, 'Retrieving census block groups from CitySDK'); const censusDataBlockGroups = await retrieveCensusData(statesCounties, 'block group'); await bar.progress(0.6, 'Blending census block groups together (can take a minute)'); let stragglerBlockGroups; [mixedShapeData, stragglerBlockGroups] = await mixCensusIntoShapefile(mixedShapeData, tigerGeoBlockGroups, censusDataBlockGroups, [['state', 'STATE'], ['county', 'COUNTY'], ['tract', 'TRACT'], ['block-group', 'BLKGRP']], false); const stragglerBlockGroupStrings = stragglerBlockGroups.map(x => `${x.properties.STATE}-${x.properties.COUNTY}-${x.properties.TRACT}-${x.properties.BLKGRP}`); // Get blocks from stragglers await bar.progress(0.7, 'Fetching census blocks that overlapped from TIGERweb'); const tigerGeoBlocksAll = await tigerPoly(hull, BLOCK); const tigerGeoBlocks = turf.featureCollection(tigerGeoBlocksAll.features.filter(x => stragglerBlockGroupStrings.includes(`${x.properties.STATE}-${x.properties.COUNTY}-${x.properties.TRACT}-${x.properties.BLKGRP}`))); await bar.progress(0.8, 'Retrieving census blocks from CitySDK'); const censusDataBlocks = await retrieveCensusData(statesCounties, 'block'); await bar.progress(0.9, 'Blending census blocks together (can take a few minutes)'); mixedShapeData = (await mixCensusIntoShapefile(mixedShapeData, tigerGeoBlocks, censusDataBlocks))[0]; bar.resolve({ hull, tigerGeoBlocks, tigerGeoBlockGroups, tigerGeoTracts, statesCounties, mixedShapeData }); }32:Tdc0,{ if (resultData == null) return 'Waiting to render'; // Clear layers/listeners removeAllLayers(); removeAllListeners(); clearPopup(); // Add all sources addSource(map, 'source', resultData.mixedShapeData); if (showBlocks) { addSource(map, 'blocks', resultData.tigerGeoBlocks); addSource(map, 'blockgroups', resultData.tigerGeoBlockGroups); addSource(map, 'tracts', resultData.tigerGeoTracts); } if (showConvex) { addSource(map, 'hull', resultData.hull); } // Add all layers if (showConvex) { addLayer(map, 'hull', { 'type': 'fill', 'source': 'hull', 'layout': {}, 'paint': { 'fill-color': 'rgba(0, 0, 0, 0.10)', }, }); } addLayer(map, 'fill', { 'type': 'fill', 'source': 'source', 'layout': {}, 'paint': { 'fill-color': [ 'case', ['boolean', ['feature-state', 'hover'], false], 'rgba(255, 128, 0, 0.8)', 'rgba(255, 128, 0, 0.3)', ] }, }); addLayer(map, 'line', { 'type': 'line', 'source': 'source', 'layout': {}, 'paint': { 'line-color': 'black', 'line-width': 2, }, }); if (showBlocks) { addLayer(map, 'blocklines', { 'type': 'line', 'source': 'blocks', 'layout': {}, 'paint': { 'line-color': 'rgba(255, 0, 255, 0.5)', 'line-width': 0.5, }, }); addLayer(map, 'blockgrouplines', { 'type': 'line', 'source': 'blockgroups', 'layout': {}, 'paint': { 'line-color': 'rgba(205, 0, 255, 0.5)', 'line-width': 0.5, }, }); addLayer(map, 'tractlines', { 'type': 'line', 'source': 'tracts', 'layout': {}, 'paint': { 'line-color': 'rgba(155, 0, 255, 0.5)', 'line-width': 0.5, }, }); } let hoveredId = null; mapboxPopup.popup = new mapboxgl.Popup({ closeButton: true, closeOnClick: true }); addListener('click', 'fill', e => { if (e.features.length > 0) { mapboxPopup.popup.setLngLat(e.lngLat).setHTML(` ${censusVariables.map(([_, name]) => ` `).join('\n')}

${name}

${e.features[0].properties[`__census_${name}`].toLocaleString(undefined, {maximumFractionDigits: 0})}

(${(e.features[0].properties[`__census_pct_${name}`] * 100).toLocaleString(undefined, {maximumFractionDigits: 1})}%)

`).addTo(map); } }); addListener('mousemove', 'fill', e => { if (e.features.length > 0) { if (hoveredId) { map.setFeatureState( { source: 'source', id: hoveredId }, { hover: false } ); } hoveredId = e.features[0].id; map.setFeatureState( { source: 'source', id: hoveredId }, { hover: true } ); } }); addListener('mouseleave', 'fill', function() { if (hoveredId) { map.setFeatureState( { source: 'source', id: hoveredId }, { hover: false } ); } hoveredId = null; }); return 'Rendered'; }33:T659,esriStyle = { // Adapted from https://gist.github.com/jgravois/51e2b30e3d6cf6c00f06b263a29108a2 // https://esri.com/arcgis-blog/products/arcgis-living-atlas/mapping/new-osm-vector-basemap const styleUrl = "https://www.arcgis.com/sharing/rest/content/items/3e1a00aeae81496587988075fe529f71/resources/styles/root.json"; // first fetch the esri style file // https://www.mapbox.com/mapbox-gl-js/style-spec const response = await fetch(styleUrl); const style = await response.json(); // next fetch metadata for the raw tiles const metadataUrl = style.sources.esri.url; const metadataResponse = await fetch(metadataUrl); const metadata = await metadataResponse.json(); function format (style, metadata, styleUrl) { // ArcGIS Pro published vector services dont prepend tile or tileMap urls with a / style.sources.esri = { type: 'vector', scheme: 'xyz', tilejson: metadata.tilejson || '2.0.0', format: (metadata.tileInfo && metadata.tileInfo.format) || 'pbf', /* mapbox-gl-js does not respect the indexing of esri tiles because we cache to different zoom levels depending on feature density, in rural areas 404s will still be encountered. more info: https://github.com/mapbox/mapbox-gl-js/pull/1377 */ // index: metadata.tileMap ? style.sources.esri.url + '/' + metadata.tileMap : null, maxzoom: 15, tiles: [ style.sources.esri.url + '/' + metadata.tiles[0] ], description: metadata.description, name: metadata.name }; return style; } return format(style, metadata, styleUrl); }34:Tb71,async function mixCensusIntoShapefile(shapeData, tigerGeo, blockData, scope=[['state', 'STATE'], ['county', 'COUNTY'], ['tract', 'TRACT'], ['block', 'BLOCK']], acceptPartial=true, clear=false) { const geoId = [shapeData.features.map(x => x.geometry.bbox), tigerGeo.features.map(x => x.geometry.bbox), acceptPartial, clear]; const hash = sha512(JSON.stringify(geoId)); const key = `census-shape-${hash}`; const cached = await localForage.getItem(key); if (cached != null) { return JSON.parse(cached); } const areas = tigerGeo.features.map(x => polygonArea.geometry(x.geometry)); const shapeDataCensusResults = {}; const stragglers = []; bboxizeGeojson(shapeData); for (let i = 0; i < shapeData.features.length; i++) { const feature = shapeData.features[i]; // Clear census results if (clear) { for (let k = 0; k < censusVariables.length; k++) { const [_, name] = censusVariables[k]; const propertyKey = `__census_${name}`; feature.properties[propertyKey] = 0; } } for (let j = 0; j < tigerGeo.features.length; j++) { const tigerFeature = tigerGeo.features[j]; const bbox1 = feature.geometry.bbox; const bbox2 = tigerFeature.geometry.bbox; if (bbox1[2] < bbox2[0] || bbox1[0] > bbox2[2] || bbox1[1] > bbox2[3] || bbox1[3] < bbox2[1]) continue; let result; try { result = clipping.intersection(feature.geometry.coordinates, tigerFeature.geometry.coordinates); } catch (e) { result = turf.intersect(feature, tigerFeature); if (result != null && result.length > 0) { result = result.geometry.coordinates; } } if (result == null || result.length == 0) continue; const area = polygonArea.geometry(turf.multiPolygon(result).geometry) / areas[j]; if (closeTo(area, 0)) continue; if (!acceptPartial && !closeTo(area, 1)) { stragglers.push(tigerFeature); continue; } const censusData = ensureOne(blockData.filter(x => scope.every(z => x[z[0]] == tigerFeature.properties[z[1]]))); // Add census results in for (let k = 0; k < censusVariables.length; k++) { const [key, name] = censusVariables[k]; const propertyKey = `__census_${name}`; feature.properties[propertyKey] = (feature.properties[propertyKey] || 0) + censusData[key] * area; } } // Get census percents for (let k = 0; k < censusVariables.length; k++) { const [key, name] = censusVariables[k]; const propertyKey = `__census_pct_${name}`; feature.properties[propertyKey] = feature.properties[`__census_${censusVariables[k][1]}`] / feature.properties[`__census_${censusVariables[0][1]}`]; 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`;\n\n // Give the container dimensions.\n yield container;\n\n // Create the \\`map\\` object with the mapboxgl.Map constructor, referencing\n // the container div\n console.log('loading mapboxgl');\n let map = new mapboxgl.Map({\n container,\n style: esriStyle,\n center: shapeDataEmpty ? [-74.0060, 40.7128] : turf.center(shapeData).geometry.coordinates,\n customAttribution: \"© OpenStreetMap contributors, map layer by Esri\",\n zoom: 11,\n });\n\n // Wait until the map loads.\n console.log('waiting map load');\n map.on(\"load\", () => {\n container.value = map;\n container.dispatchEvent(new CustomEvent(\"input\"));\n });\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":1064,"value":"{\n if (mixedShapeData == null) return '';\n const button = html``;\n button.onclick = () => shpWrite.download(mixedShapeData);\n return button;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":1073,"value":"{\n if (mixedShapeData == null) return '';\n return createJsonDownloadButton(shapeData, 'shapefile.json', 'Download GeoJSON');\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":1085,"value":"mixedShapeData = resultData == null ? null : resultData.mixedShapeData","pinned":false,"hidden":false,"mode":"ojs"},{"id":31,"value":"$32","pinned":false,"hidden":false,"mode":"ojs"},{"id":448,"value":"censusVariables = [\n // https://api.census.gov/data/2010/dec/sf1/variables.html\n ['P003001', 'Total'],\n ['P003002', 'White'],\n ['P003003', 'Black'],\n ['P003004', 'American Indian / Alaska Native'],\n ['P003005', 'Asian'],\n ['P003006', 'Native Hawaiian / Pacific Islander'],\n ['P003007', 'Other'],\n ['P003008', 'Mixed'],\n ['P004003', 'Hispanic or Latino'],\n]","pinned":true,"hidden":false,"mode":"ojs"},{"id":441,"value":"async function retrieveCensusData(statesCounties, geoHierarchy) {\n if (statesCounties == null) return null;\n return flatten(await Promise.all(statesCounties.map(x => getCensusData(x[0], x[1], censusVariables.map(x => x[0]), geoHierarchy, localStorage['census-api-key'] || undefined))));\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":934,"value":"function getStatesCounties(tigerGeo) {\n if (tigerGeo == null) return null;\n const results = {};\n tigerGeo.features.forEach(feature => {\n const key = `${feature.properties.STATE}-${feature.properties.COUNTY}`;\n results[key] = true;\n });\n return Object.keys(results).map(x => x.split('-'));\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":834,"value":"shapeDataEmpty = shapeData.features.length == 0","pinned":false,"hidden":false,"mode":"ojs"},{"id":954,"value":"showBlocks = true","pinned":false,"hidden":false,"mode":"ojs"},{"id":740,"value":"showConvex = true // whether to show the convex hull","pinned":false,"hidden":false,"mode":"ojs"},{"id":830,"value":"shapeData = {\n if (shapefilePre != null && subfile != null && subfile != '') {\n return shapefilePre[parseInt(subfile)];\n } else if (shapefilePre != null && !Array.isArray(shapefilePre)) {\n return shapefilePre;\n } else {\n return {\n type: \"FeatureCollection\",\n features: [],\n };\n }\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":792,"value":"exampleData = ({\n 'seattle_police': {\n file: FileAttachment('SeattlePolice.zip'),\n },\n 'dc_police': {\n file: FileAttachment('DCPolice.zip'),\n },\n 'durham_police': {\n file: FileAttachment('DurhamPolice.zip'),\n fn: x => x[0],\n },\n 'nyc_police': {\n file: FileAttachment('NYCPolice.zip'),\n },\n 'cambridge_police': {\n file: FileAttachment('CambridgePolice.zip'),\n },\n})","pinned":false,"hidden":false,"mode":"ojs"},{"id":209,"value":"!shapeDataEmpty && map.flyTo({center: turf.center(shapeData).geometry.coordinates})","pinned":false,"hidden":false,"mode":"ojs"},{"id":177,"value":"md`## Imports, helpers`","pinned":false,"hidden":false,"mode":"ojs"},{"id":189,"value":"md`### Supporting interactive map code`","pinned":false,"hidden":false,"mode":"ojs"},{"id":777,"value":"shapefilePre = {\n let file = null;\n if (examples != null && examples != '') {\n // An example is selected\n file = await exampleData[examples].file;\n } else {\n if (inputFile != null && inputFile != '') {\n file = inputFile;\n }\n }\n \n if (file == null) return null;\n \n const arrayBuffer = await file.arrayBuffer();\n const results = await shapefile(arrayBuffer);\n if (examples != null && examples != '' && exampleData[examples].fn != null) {\n return exampleData[examples].fn(results);\n }\n return results;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":27,"value":"function addSource(map, name, data) {\n const source = map.getSource(name);\n if (source != null) {\n map.removeSource(name);\n }\n map.addSource(name, {\n type: 'geojson',\n data,\n generateId: true,\n });\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":677,"value":"function clearPopup() {\n if (mapboxPopup.popup != null) {\n mapboxPopup.popup.remove();\n mapboxPopup.popup = null;\n }\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":643,"value":"mapboxPopup = ({})","pinned":false,"hidden":false,"mode":"ojs"},{"id":154,"value":"function addListener(event, layer, fn) {\n listeners.push([event, layer, fn]);\n map.on(event, layer, fn);\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":156,"value":"function removeAllListeners() {\n listeners.forEach(([event, layer, fn]) => map.off(event, layer, fn));\n while (listeners.length) listeners.pop();\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":25,"value":"function addLayer(map, name, properties, behind=undefined) {\n if (map.getLayer(name) != null) {\n // Remove the layer first if needed\n map.removeLayer(name);\n }\n map.addLayer({id: name, ...properties}, behind);\n layers[name] = true;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":23,"value":"function removeAllLayers() {\n Object.keys(layers).forEach(name => {\n if (map.getLayer(name) != null) {\n map.removeLayer(name);\n }\n delete layers[name];\n });\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":21,"value":"layers = ({})","pinned":false,"hidden":false,"mode":"ojs"},{"id":161,"value":"listeners = ([])","pinned":false,"hidden":false,"mode":"ojs"},{"id":70,"value":"$33","pinned":false,"hidden":false,"mode":"ojs"},{"id":342,"value":"md`### Supporting geoanalysis code`","pinned":false,"hidden":false,"mode":"ojs"},{"id":645,"value":"$34","pinned":false,"hidden":false,"mode":"ojs"},{"id":989,"value":"function closeTo(a, b) {\n return Math.abs(a - b) < 0.0001;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":625,"value":"function ensureOne(x) {\n if (x.length != 1) throw new Error(`Invalid: expecting 1 (${x})`);\n return x[0];\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":453,"value":"function flatten(x) {\n const results = [];\n x.forEach(y => y.forEach(z => results.push(z)));\n return results;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":498,"value":"function bboxize(coordinates) {\n let xMin = null;\n let xMax = null;\n let yMin = null;\n let yMax = null;\n\n if (Array.isArray(coordinates[0])) {\n for (let i = 0; i < coordinates.length; i++) {\n const newBbox = bboxize(coordinates[i]);\n if (newBbox != null) {\n if (xMin == null || newBbox.xMin < xMin) xMin = newBbox.xMin;\n if (xMax == null || newBbox.xMax > xMin) xMax = newBbox.xMax;\n if (yMin == null || newBbox.yMin < yMin) yMin = newBbox.yMin;\n if (yMax == null || newBbox.yMax > yMin) yMax = newBbox.yMax;\n }\n }\n } else {\n const [x, y] = coordinates;\n return {xMin: x, xMax: x, yMin: y, yMax: y};\n }\n \n if (xMin == null) return null;\n return {xMin, xMax, yMin, yMax};\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":500,"value":"function bboxizeGeojson(geojson) {\n for (let i = 0; i < geojson.features.length; i++) {\n const bbox = bboxize(geojson.features[i].geometry.coordinates);\n geojson.features[i].geometry.bbox = [bbox.xMin, bbox.yMin, bbox.xMax, bbox.yMax];\n }\n return geojson;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":361,"value":"async function queryCensusBlocks(geojson) {\n // Get a sub-polygon to roughly query only the needed blocks\n const bbox = turf.bbox(geojson);\n const boundingGeometry = boundingQuadTree(geojson);\n \n // Request from TigerWeb\n const request = await fetch(`https://tigerweb.geo.census.gov/arcgis/rest/services/TIGERweb/tigerWMS_Census2010/MapServer/18/query?outFields=*&geometry=${encodeURIComponent(JSON.stringify(esri.geojsonToArcGIS(boundingGeometry).geometry))}&geometryType=esriGeometryPolygon&inSR=4326&outSR=4326&outFields=*&f=json`);\n const json = await request.json();\n return json;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":265,"value":"function polygonFromBbox(bbox) {\n return turf.polygon([[[bbox[0], bbox[1]], [bbox[2], bbox[1]], [bbox[2], bbox[3]], [bbox[0], bbox[3]], [bbox[0], bbox[1]]]]);\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":286,"value":"function intersects(polyOrMultipoly, bboxPoly) {\n if (polyOrMultipoly.type == 'FeatureCollection') {\n return polyOrMultipoly.features.some(feature => intersects(feature, bboxPoly));\n } else if (polyOrMultipoly.type == 'Feature') {\n return intersects(polyOrMultipoly.geometry, bboxPoly);\n } else if (polyOrMultipoly.type == 'MultiPolygon') {\n return polyOrMultipoly.coordinates.some(poly => intersects(turf.polygon(poly), bboxPoly));\n } else if (polyOrMultipoly.type == 'Polygon') {\n return turf.intersect(polyOrMultipoly, bboxPoly) != null;\n } else {\n throw new Error(`Unsupported intersection: ${polyOrMultipoly}`);\n }\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":516,"value":"function intersect(poly1, poly2) {\n const bbox1 = poly1.geometry.bbox;\n const bbox2 = poly2.geometry.bbox;\n \n if (bbox1[2] < bbox2[0] || bbox1[0] > bbox2[2] || bbox1[1] > bbox2[3] || bbox1[3] < bbox2[1]) return null;\n return turf.intersect(poly1, poly2);\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":910,"value":"function convexHull(features) {\n return turf.convex(features);\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":366,"value":"async function boundingQuadTree(shape) {\n const hash = sha512(JSON.stringify(shape));\n const key = `quad-${hash}`;\n const cached = await localForage.getItem(key);\n if (cached != null) {\n return JSON.parse(cached);\n }\n \n const union = polygonUnion(shape.features);\n const result = polygonUnion(quadTree(union));\n await localForage.setItem(key, JSON.stringify(result));\n return result;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":859,"value":"function polygonUnion(polygons) {\n let result = polygons[0].geometry.coordinates;\n for (let i = 1; i < polygons.length; i++) {\n try {\n result = clipping.union(result, polygons[i].geometry.coordinates);\n } catch (e) {\n // Use turf\n result = turfUnion(turf.multiPolygon(result), polygons[i]).geometry.coordinates;\n }\n }\n return turf.multiPolygon(result);\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":877,"value":"turfUnion = {\n return (await require('https://bundle.run/@turf/union@6.0.3')).default;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":293,"value":"function quadTree(featureCollection, iterations=3, bbox=null) {\n console.log(featureCollection);\n if (bbox == null) bbox = turf.bbox(featureCollection);\n const results = [];\n const quartiles = getQuarters(bbox);\n if (iterations > 0) {\n quartiles.forEach(quartile => {\n const quartileBbox = polygonFromBbox(quartile);\n if (intersects(featureCollection, quartileBbox)) {\n quadTree(featureCollection, iterations - 1, quartile).forEach(poly => results.push(poly));\n }\n });\n } else {\n const polyBbox = polygonFromBbox(bbox);\n if (intersects(featureCollection, polyBbox)) {\n results.push(polyBbox);\n }\n }\n return results;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":291,"value":"function getQuarters(bbox) {\n const midX = (bbox[0] + bbox[2]) / 2;\n const midY = (bbox[1] + bbox[3]) / 2;\n return [\n [bbox[0], bbox[1], midX, midY], // Top-left\n [midX, bbox[1], bbox[2], midY], // Top-right\n [bbox[0], midY, midX, bbox[3]], // Bottom-left\n [midX, midY, bbox[2], bbox[3]], // Bottom-right\n ];\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":373,"value":"md`### Supporting census code`","pinned":false,"hidden":false,"mode":"ojs"},{"id":380,"value":"getCensusData = async (state, county, variables=[], hierarchy, statsKey=null, year=2010) => {\n return await census({\n vintage: year,\n geoHierarchy: {\n state,\n county,\n [hierarchy]: \"*\",\n },\n sourcePath: [\"dec\", \"sf1\"],\n values: variables,\n statsKey\n });\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":385,"value":"async function tigerPoly(geometry, requestedGeometry) {\n // Try to fetch from cache first\n const hash = sha512(JSON.stringify([geometry, requestedGeometry]));\n const key = `tiger-${hash}`;\n const cached = await localForage.getItem(key);\n if (cached != null) {\n return JSON.parse(cached);\n }\n\n // Not cached. Fetch from census\n const response = await fetch(`https://tigerweb.geo.census.gov/arcgis/rest/services/TIGERweb/tigerWMS_Census2010/MapServer/${requestedGeometry}/query?outFields=*&geometry=${encodeURIComponent(JSON.stringify(esri.geojsonToArcGIS(geometry).geometry))}&geometryType=esriGeometryPolygon&inSR=4326&outSR=4326&outFields=*&f=json`);\n const responseJson = await response.json();\n const blocks = bboxizeGeojson(esri.arcgisToGeoJSON(responseJson));\n await localForage.setItem(key, JSON.stringify(blocks));\n return blocks;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":970,"value":"TRACT = 14","pinned":false,"hidden":false,"mode":"ojs"},{"id":972,"value":"BLOCK_GROUP = 16","pinned":false,"hidden":false,"mode":"ojs"},{"id":967,"value":"BLOCK = 18","pinned":false,"hidden":false,"mode":"ojs"},{"id":381,"value":"// Load CitySDK from the GitHub page\ncensus = {\n const census = await require('https://uscensusbureau.github.io/citysdk/assets/citysdk.js').catch(() => window.census);\n return params => new Promise(async (resolve, reject) => {\n // Try to fetch from cache first\n const jsonParams = JSON.stringify(params);\n const key = `census-${jsonParams}`;\n const cached = await localForage.getItem(key);\n if (cached != null) {\n return resolve(JSON.parse(cached));\n }\n \n // Not cached. Fetch from census\n census(\n params,\n async (err, res) => {\n if (err != null) return reject(err);\n \n // Remove stats key from response\n delete res.statsKey;\n \n // Cache compressed version\n const jsonResponse = JSON.stringify(res);\n await localForage.setItem(key, jsonResponse);\n \n // Return response\n return resolve(res);\n }\n );\n });\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":191,"value":"md`### Requirements`","pinned":false,"hidden":false,"mode":"ojs"},{"id":1074,"value":"import { createJsonDownloadButton } from \"@trebor/download-json\"","pinned":false,"hidden":false,"mode":"ojs"},{"id":1058,"value":"shpWrite = require(await FileAttachment('shpwrite.js').url())","pinned":false,"hidden":false,"mode":"ojs"},{"id":6,"value":"shapefile = require('https://unpkg.com/shpjs@latest/dist/shp.js')","pinned":false,"hidden":false,"mode":"ojs"},{"id":558,"value":"polygonArea = require('https://bundle.run/@mapbox/geojson-area@0.2.2')","pinned":false,"hidden":false,"mode":"ojs"},{"id":534,"value":"clipping = require('martinez-polygon-clipping')","pinned":false,"hidden":false,"mode":"ojs"},{"id":243,"value":"esri = require('@esri/arcgis-to-geojson-utils')","pinned":false,"hidden":false,"mode":"ojs"},{"id":2,"value":"mapboxgl = {\n const gl = await require(\"mapbox-gl@1.10.0\");\n const href = await require.resolve(\"mapbox-gl@0.49/dist/mapbox-gl.css\");\n document.head.appendChild(html``);\n return gl;\n}","pinned":false,"hidden":false,"mode":"ojs"},{"id":922,"value":"import {progress} from '@freedmand/progress'","pinned":false,"hidden":false,"mode":"ojs"},{"id":856,"value":"turf = require('@turf/turf')","pinned":false,"hidden":false,"mode":"ojs"},{"id":806,"value":"import {fileInput} from \"@mbostock/file-input-with-initial-value\"","pinned":false,"hidden":false,"mode":"ojs"},{"id":387,"value":"sha512 = require('js-sha512')","pinned":false,"hidden":false,"mode":"ojs"},{"id":376,"value":"localForage = require('localforage')","pinned":false,"hidden":false,"mode":"ojs"}],"files":"$W35","stdlib":"1","titling":"auto"}