This example shows how to use the d3-tribin plugin for triangular binning. 2,000 random points with a normal distribution are binned into hexagons; color encodes the number of points that fall into each bin. You can also use area encoding. Inspired by d3-hexbin by Mike Bostock.
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February 20, 2018 10:34
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Triangular Binning (Color)
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| license: gpl-3.0 |
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| (function (global, factory) { | |
| typeof exports === 'object' && typeof module !== 'undefined' ? factory(exports) : | |
| typeof define === 'function' && define.amd ? define(['exports'], factory) : | |
| (factory((global.d3 = global.d3 || {}))); | |
| }(this, function (exports) { 'use strict'; | |
| var sqrt3 = Math.sqrt(3); | |
| var thirdPi = Math.PI / 3; | |
| var angles = [0, thirdPi * 2, thirdPi * 4]; | |
| function pointX(d) { | |
| return d[0]; | |
| } | |
| function pointY(d) { | |
| return d[1]; | |
| } | |
| function tribin() { | |
| var s, | |
| inR, | |
| outR, | |
| h, | |
| x = pointX, | |
| y = pointY; | |
| function tribin(points) { | |
| var binsById = {}, | |
| bins = [], | |
| i, | |
| n = points.length; | |
| for (i = 0; i < n; ++i) { | |
| if (isNaN(px = +x.call(null, point = points[i], i, points)) || isNaN(py = +y.call(null, point, i, points))) continue; | |
| var point, | |
| px, | |
| py, | |
| row = Math.floor(py / h), | |
| rowIsOdd = row % 2 == 1, | |
| col = (rowIsOdd ? Math.floor((px + s / 2) / s) : Math.floor(px / s)), | |
| offY = row * h, | |
| offX = (rowIsOdd ? col * s - s / 2 : col * s), | |
| relY = py - offY, | |
| relX = px - offX, | |
| binX = offX + s / 2, | |
| binY = offY + outR, | |
| binRotation = 0, | |
| triangleCol = col * 2 + 1, | |
| triangleRow = row, | |
| m = h / (s / 2); | |
| if (relY < (-m * relX) + h) { | |
| triangleCol--; | |
| binX = offX; | |
| binY = offY + inR; | |
| binRotation = Math.PI; | |
| } else if (relY < (m * relX) - h) { | |
| triangleCol++; | |
| binX = offX + s; | |
| binY = offY + inR; | |
| binRotation = Math.PI; | |
| } | |
| var id = triangleRow + "-" + triangleCol, | |
| bin = binsById[id]; | |
| if (bin) bin.push(point); | |
| else { | |
| bins.push(bin = binsById[id] = [point]); | |
| bin.x = binX; | |
| bin.y = binY; | |
| bin.rotation = binRotation; | |
| } | |
| } | |
| return bins; | |
| } | |
| function triangle(side, rotation) { | |
| var x0 = 0, y0 = 0, r = side * sqrt3 / 3; | |
| return angles.map(function(angle) { | |
| var x1 = Math.sin(angle + rotation) * r, | |
| y1 = -Math.cos(angle + rotation) * r, | |
| dx = x1 - x0, | |
| dy = y1 - y0; | |
| x0 = x1, y0 = y1; | |
| return [dx, dy]; | |
| }); | |
| } | |
| tribin.triangle = function(side, rotation, center) { | |
| side = (side == null ? s : +side), | |
| rotation = (rotation == null ? 0 : +rotation); | |
| var moveCenter = (center == null ? "" : "M" + center[0] + "," + center[1]); | |
| return moveCenter + "m" + triangle(side, rotation).join("l") + "z"; | |
| } | |
| tribin.triangleFromBin = function(d, side) { | |
| side = (side == null ? s : +side); | |
| return tribin.triangle(side, d.rotation, [d.x, d.y]); | |
| } | |
| tribin.x = function(_) { | |
| return arguments.length ? (x = _, tribin) : x; | |
| }; | |
| tribin.y = function(_) { | |
| return arguments.length ? (y = _, tribin) : y; | |
| }; | |
| tribin.side = function(_) { | |
| return arguments.length ? (s = +_, inR = s * sqrt3 / 6, outR = s * sqrt3 / 3, h = inR + outR, tribin) : s; | |
| }; | |
| return tribin.side(1); | |
| }; | |
| exports.tribin = tribin; | |
| Object.defineProperty(exports, '__esModule', { value: true }); | |
| })); |
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| <!DOCTYPE html> | |
| <style> | |
| .hexagon { | |
| stroke: white; | |
| stroke-width: 0.5px; | |
| } | |
| </style> | |
| <svg width="960" height="500"></svg> | |
| <script src="https://d3js.org/d3.v4.min.js"></script> | |
| <script src="d3-tribin.js"></script> | |
| <script> | |
| var svg = d3.select("svg"), | |
| margin = {top: 20, right: 20, bottom: 30, left: 40}, | |
| width = +svg.attr("width") - margin.left - margin.right, | |
| height = +svg.attr("height") - margin.top - margin.bottom, | |
| g = svg.append("g").attr("transform", "translate(" + margin.left + "," + margin.top + ")"); | |
| var randomX = d3.randomNormal(width / 2, 80), | |
| randomY = d3.randomNormal(height / 2, 80), | |
| points = d3.range(2000).map(function() { return [randomX(), randomY()]; }); | |
| var triangleSide = 35, | |
| tribin = d3.tribin().side(triangleSide), | |
| bins = tribin(points), | |
| binsLength = bins.map(function (bin) { return bin.length; }), | |
| scaleColor = d3.scaleSequential(d3.interpolateLab("white", "steelblue")).domain([0, d3.max(binsLength)]); | |
| var x = d3.scaleLinear() | |
| .domain([0, width]) | |
| .range([0, width]); | |
| var y = d3.scaleLinear() | |
| .domain([0, height]) | |
| .range([height, 0]); | |
| g.append("clipPath") | |
| .attr("id", "clip") | |
| .append("rect") | |
| .attr("width", width) | |
| .attr("height", height); | |
| g.append("g") | |
| .attr("class", "hexagon") | |
| .attr("clip-path", "url(#clip)") | |
| .selectAll("path") | |
| .data(bins) | |
| .enter().append("path") | |
| .attr("d", function(d) { return tribin.triangleFromBin(d); }) | |
| .attr("fill", function(d) { return scaleColor(d.length); }); | |
| g.append("g") | |
| .attr("class", "axis axis--y") | |
| .call(d3.axisLeft(y).tickSizeOuter(-width)); | |
| g.append("g") | |
| .attr("class", "axis axis--x") | |
| .attr("transform", "translate(0," + height + ")") | |
| .call(d3.axisBottom(x).tickSizeOuter(-height)); | |
| </script> |
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