Mapping distance between census tracts using d3.geo.distance between the two centroids. Click on a census tract to show distance for all others by color.
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April 16, 2016 03:00
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NYC Map - Distance between Census Tracts by Color
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| .tpath { | |
| /*fill:#ccc;*/ | |
| stroke:#ccc | |
| } | |
| .census-centr-on { | |
| fill:red; | |
| } | |
| .census-centr-off { | |
| fill:none; | |
| } | |
| </style> | |
| <body> | |
| <script src="http://d3js.org/d3.v3.min.js"></script> | |
| <script src="http://d3js.org/topojson.v1.min.js"></script> | |
| <script src="map.js"></script> |
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| var width = 750, | |
| height = 500; | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width) | |
| .attr("height", height); | |
| var test; | |
| d3.json("nyccensus.json", function(error, nyc) { | |
| if (error) {return console.error(error)} | |
| var subunits = topojson.feature(nyc, nyc.objects.census) | |
| test = subunits; | |
| // | |
| var projection = d3.geo.mercator() | |
| .center([-73.94, 40.70]) | |
| .scale(50000) | |
| .translate([width / 2, height / 2]) | |
| // | |
| var path = d3.geo.path() | |
| .projection(projection); | |
| // | |
| features = subunits.features | |
| features.forEach(function(feature, i) { | |
| feature.centroid = path.centroid(feature); | |
| if (feature.centroid.some(isNaN)) feature.centroid = null; // off the map | |
| }); | |
| color = d3.scale.sqrt() | |
| .domain([0,0.007]) | |
| // .range(["#deebf7","#08306b"]) | |
| .range(["#fff","#000"]) | |
| var tracts = svg.selectAll('.tcontainer') | |
| .data(features) | |
| .enter() | |
| .append("g") | |
| .attr('class','tcontainer') | |
| .append("path") | |
| .attr('class','tpath') | |
| .attr("d", path) | |
| .attr("fill",'#fff') | |
| .on("click", function(d){ | |
| dcenter(this.parentNode) | |
| }); | |
| function dcenter(tct) { | |
| reset(); | |
| var hl_circ = d3.select(tct).selectAll('circle') | |
| .attr('class','census-centr-on'); | |
| var ref_coord = projection.invert(hl_circ.datum().centroid); | |
| tracts = set_new_loc(ref_coord) | |
| } | |
| function reset() { | |
| d3.selectAll('.census-centr-on') | |
| .attr('class','census-centr-off'); | |
| } | |
| function set_new_loc(coords) { | |
| d3.selectAll('.tpath') | |
| .attr('fill',function(d){ | |
| return color(d3.geo.distance(coords,projection.invert(d.centroid))) | |
| }) | |
| } | |
| var dots = svg.selectAll('.tcontainer') | |
| .append('circle') | |
| .attr('class','census-centr-off') | |
| .attr('transform',function(d){ | |
| return 'translate (' + d.centroid[0] + ',' +d.centroid[1] + ')' | |
| }) | |
| .attr('r',2) | |
| }) |
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