Click-hold to select geographic units whose centroids are within the circular area surrounding the cursor.
Last active
November 28, 2015 03:36
-
-
Save armollica/94bfb37d81234ad91ced to your computer and use it in GitHub Desktop.
Circular Geography Selection
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| <!DOCTYPE html> | |
| <html> | |
| <head> | |
| <meta charset="utf-8"> | |
| <title>Circular Geography Selection</title> | |
| <style> | |
| body { | |
| font-family: "Helvetica Neue", Helvetica, Arial, sans-serif; | |
| margin: auto; | |
| position: relative; | |
| width: 960px; | |
| } | |
| button { | |
| position: absolute; | |
| right: 10px; | |
| top: 10px; | |
| } | |
| canvas { | |
| cursor: crosshair; | |
| } | |
| </style> | |
| </head> | |
| <body> | |
| <button class="reset">Reset</button> | |
| <script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.6/d3.min.js" charset="utf-8"></script> | |
| <script src="https://cdnjs.cloudflare.com/ajax/libs/topojson/1.6.19/topojson.min.js"></script> | |
| <script> | |
| var width = 960, | |
| height = 500, | |
| clickRadius = 4; | |
| var projection = d3.geo.albers() | |
| .scale(1000); | |
| var canvas = d3.select("body").append("canvas") | |
| .attr('width', width) | |
| .attr('height', height); | |
| var context = canvas.node().getContext('2d'); | |
| var path = d3.geo.path() | |
| .projection(projection) | |
| .context(context); | |
| var button = d3.select("button.reset"); | |
| d3.json('us.json', function(error, us) { | |
| if (error) throw error; | |
| var counties = topojson.feature(us, us.objects.counties); | |
| counties.features.forEach(function(feature) { | |
| feature.properties.centroid = path.centroid(feature); | |
| }); | |
| path(counties); | |
| context.fillStyle = "#a3c1ad"; | |
| context.fill(); | |
| context.strokeStyle = "#fff"; | |
| context.lineWidth = .5; | |
| context.stroke(); | |
| button | |
| .on('click', function() { | |
| path(counties); | |
| context.fillStyle = "#a3c1ad"; | |
| context.fill(); | |
| context.stroke(); | |
| }); | |
| canvas | |
| .on('mousemove', function() { | |
| var e = d3.event, | |
| cx = e.layerX, | |
| cy = e.layerY; | |
| if (e.buttons == 1) { | |
| var featuresInRadius = counties.features.filter(function(feature) { | |
| var centroid = feature.properties.centroid, | |
| x = centroid[0], | |
| y = centroid[1]; | |
| return Math.sqrt(Math.pow(x - cx, 2) + Math.pow(y - cy, 2)) | |
| <= Math.pow(clickRadius, 2); | |
| }); | |
| featuresInRadius = { | |
| type: "FeatureCollection", | |
| features: featuresInRadius | |
| }; | |
| context.beginPath(); | |
| path(featuresInRadius); | |
| context.fillStyle = "#5f9ea0"; | |
| context.fill(); | |
| context.stroke(); | |
| } | |
| }); | |
| }); | |
| </script> | |
| </body> | |
| </html> |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment