This example is an extension of Mike Bostock’s tutorial Lets Make a Map that implements automatic label placement using the force layout and multiple foci. The centroid of each feature will define a foci of the force. This foci will attract the label that correspond to that feature (and ignore the others). The labels will repel themselves to avoid overlapping.
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February 8, 2017 12:54
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Automatic Label Placement
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| <!DOCTYPE html> | |
| <html lang="en"> | |
| <head> | |
| <meta charset="UTF-8"/> | |
| <title>Automatic Label Placement</title> | |
| <script src="http://d3js.org/d3.v3.min.js"></script> | |
| <script src="http://d3js.org/topojson.v1.min.js"></script> | |
| <style> | |
| .subunit.SCT { fill: #ddc; } | |
| .subunit.WLS { fill: #cdd; } | |
| .subunit.NIR { fill: #cdc; } | |
| .subunit.ENG { fill: #dcd; } | |
| .subunit.IRL, | |
| .subunit-label.IRL { | |
| display: none; | |
| } | |
| .subunit-boundary { | |
| fill: none; | |
| stroke: #777; | |
| stroke-dasharray: 2,2; | |
| stroke-linejoin: round; | |
| } | |
| .subunit-boundary.IRL { | |
| stroke: #aaa; | |
| } | |
| .subunit-label { | |
| fill: #777; | |
| fill-opacity: .5; | |
| font-size: 20px; | |
| font-weight: 300; | |
| text-anchor: middle; | |
| } | |
| .place, | |
| .place-label { | |
| fill: #444; | |
| } | |
| text { | |
| font-family: "Helvetica Neue", Helvetica, Arial, sans-serif; | |
| font-size: 10px; | |
| pointer-events: none; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <script> | |
| var width = 960, | |
| height = 1160; | |
| var projection = d3.geo.albers() | |
| .center([0, 55.4]) | |
| .rotate([4.4, 0]) | |
| .parallels([50, 60]) | |
| .scale(1200 * 5) | |
| .translate([width / 2, height / 2]); | |
| var path = d3.geo.path() | |
| .projection(projection) | |
| .pointRadius(2); | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width) | |
| .attr("height", height); | |
| d3.json("uk.json", function(error, uk) { | |
| var subunits = topojson.feature(uk, uk.objects.subunits), | |
| places = topojson.feature(uk, uk.objects.places); | |
| svg.selectAll(".subunit") | |
| .data(subunits.features) | |
| .enter().append("path") | |
| .attr("class", function(d) { return "subunit " + d.id; }) | |
| .attr("d", path); | |
| svg.append("path") | |
| .datum(topojson.mesh(uk, uk.objects.subunits, function(a, b) { return a !== b && a.id !== "IRL"; })) | |
| .attr("d", path) | |
| .attr("class", "subunit-boundary"); | |
| svg.append("path") | |
| .datum(topojson.mesh(uk, uk.objects.subunits, function(a, b) { return a === b && a.id === "IRL"; })) | |
| .attr("d", path) | |
| .attr("class", "subunit-boundary IRL"); | |
| svg.selectAll(".subunit-label") | |
| .data(subunits.features) | |
| .enter().append("text") | |
| .attr("class", function(d) { return "subunit-label " + d.id; }) | |
| .attr("transform", function(d) { return "translate(" + path.centroid(d) + ")"; }) | |
| .attr("dy", ".35em") | |
| .text(function(d) { return d.properties.name; }); | |
| svg.append("path") | |
| .datum(places) | |
| .attr("d", path) | |
| .attr("class", "place"); | |
| // Place and label location | |
| var foci = [], | |
| labels = []; | |
| // Store the projected coordinates of the places for the foci and the labels | |
| places.features.forEach(function(d, i) { | |
| var c = projection(d.geometry.coordinates) | |
| foci.push({x: c[0], y: c[1]}); | |
| labels.push({x: c[0], y: c[1], label: d.properties.name}) | |
| }); | |
| // Create the force layout with a slightly weak charge | |
| var force = d3.layout.force() | |
| .nodes(labels) | |
| .charge(-20) | |
| .gravity(0) | |
| .chargeDistance(width / 8) | |
| .size([width, height]); | |
| // Append the place labels, setting their initial positions to | |
| // the feature's centroid | |
| var placeLabels = svg.selectAll('.place-label') | |
| .data(labels) | |
| .enter() | |
| .append('text') | |
| .attr('class', 'place-label') | |
| .attr('x', function(d) { return d.x; }) | |
| .attr('y', function(d) { return d.y; }) | |
| .attr('text-anchor', 'middle') | |
| .text(function(d) { return d.label; }); | |
| force.on("tick", function(e) { | |
| var k = .1 * e.alpha; | |
| labels.forEach(function(o, j) { | |
| // The change in the position is proportional to the distance | |
| // between the label and the corresponding place (foci) | |
| o.y += (foci[j].y - o.y) * k; | |
| o.x += (foci[j].x - o.x) * k; | |
| }); | |
| // Update the position of the text element | |
| svg.selectAll("text.place-label") | |
| .attr("x", function(d) { return d.x; }) | |
| .attr("y", function(d) { return d.y; }); | |
| }); | |
| force.start(); | |
| }); | |
| </script> | |
| </body> | |
| </html> |
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