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September 15, 2017 05:08
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Labeling arcs at the midpoint
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| <script src="https://d3js.org/d3.v4.min.js"></script> | |
| <body> | |
| <script> | |
| let width = 300; | |
| let height = 300; | |
| let svg = d3.select('body').append('svg') | |
| .attr('width', width) | |
| .attr('height', height) | |
| .append('g') | |
| .attr('transform', `translate(${width * 0.5}, ${height * 0.5})`); | |
| let outerRadius = 0.8 * width * 0.5, | |
| innerRadius = 0.6 * width * 0.5; | |
| let data = [ | |
| { | |
| startAngle: 0, | |
| endAngle: Math.PI * 1, | |
| name: "Cow" | |
| }, | |
| { | |
| startAngle: Math.PI * 1, | |
| endAngle: Math.PI * 1.2, | |
| name: "Banana" | |
| }, | |
| { | |
| startAngle: Math.PI * 1.2, | |
| endAngle: Math.PI * 1.8, | |
| name: "Apple" | |
| }, | |
| { | |
| startAngle: Math.PI * 1.8, | |
| endAngle: Math.PI * 2, | |
| name: "This is a long one" | |
| } | |
| ]; | |
| let color = d3.scaleOrdinal(d3.schemeCategory10); | |
| let arc = d3.arc() | |
| .outerRadius(outerRadius) | |
| .innerRadius(innerRadius) | |
| .startAngle(d => d.startAngle) | |
| .endAngle(d => d.endAngle); | |
| let bars = svg.selectAll('.bar').data(data); | |
| let barsEnter = bars.enter() | |
| .append('path') | |
| .attr('class', 'bar') | |
| bars.merge(barsEnter) | |
| .attr('d', d => arc(d)) | |
| .attr('fill', d => color(d.name)) | |
| // create arcs that wrap around the entire circle and have the midpoint | |
| // at the angle we want to center the text on | |
| let textArcData = data.map(d => { | |
| let angle = (d.startAngle + d.endAngle) * 0.5; | |
| if (angle > Math.PI / 2 && angle < Math.PI * 3 / 2) { | |
| return { | |
| startAngle: angle + Math.PI, | |
| endAngle: angle - Math.PI, | |
| lowerHalf: true, | |
| name: d.name | |
| } | |
| } else { | |
| return { | |
| startAngle: angle - Math.PI, | |
| endAngle: angle + Math.PI, | |
| lowerHalf: false, | |
| name: d.name | |
| } | |
| } | |
| }) | |
| let textArc = d3.arc() | |
| .outerRadius(outerRadius) | |
| .innerRadius(outerRadius); | |
| let textArcs = svg.selectAll('.text-arc').data(textArcData); | |
| let textArcsEnter = textArcs.enter() | |
| .append('path') | |
| .attr('class', 'text-arc') | |
| .merge(textArcs) | |
| .attr('d', d => textArc(d)) | |
| .attr('id', (d, i) => 'textarc' + i) | |
| .style("fill", "none"); | |
| svg.selectAll(".behaviorText") | |
| .data(textArcData) | |
| .enter().append("text") | |
| .attr("class", "behaviorText") | |
| .attr('dy', d => d.lowerHalf ? 14 : -4) | |
| .append("textPath") | |
| .attr("xlink:href", (d, i) => '#textarc' + i) | |
| // since the arc wraps around, a quarter of the length will be the midpoint | |
| .attr('startOffset', '25%') | |
| .style("text-anchor","middle") | |
| .text(d => d.name); | |
| </script> | |
| </body> |
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