This block demonstrates the subtle, but important, visual differences in making the area of an element proportional to it's given value rather than it's radius or length of side. For simplicity, values of 0 - 100 are used in this example.
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June 14, 2016 22:46
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Radius vs. Area
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| license: mit |
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| <!DOCTYPE html> | |
| <meta charset="utf-8"> | |
| <style> | |
| text { | |
| font: 12px sans-serif; | |
| } | |
| </style> | |
| <body> | |
| <script src="//d3js.org/d3.v3.min.js"></script> | |
| <script> | |
| var margin = { | |
| top: 50, | |
| bottom: 30, | |
| left: 50, | |
| right: 50 | |
| }; | |
| var width = 960; | |
| var height = 400; | |
| var xScale = d3.scale.linear() | |
| .domain([0, 100]) | |
| .range([margin.left, width - margin.right]); | |
| var svg = d3.select("body").append("svg") | |
| .attr("width", width) | |
| .attr("height", height); | |
| var ticks = xScale.ticks(21); | |
| var elementWidth = xScale(ticks[1]) - xScale(ticks[0]); | |
| var maxRadius = elementWidth / 2; | |
| var maxSide = Math.sqrt(Math.PI * maxRadius * maxRadius); | |
| var yScale = d3.scale.linear() | |
| .domain([0, 4]) | |
| .range([margin.top + maxRadius, height - margin.bottom - maxRadius]); | |
| var percents = svg.selectAll('g.percent') | |
| .data(ticks); | |
| var enter = percents | |
| .enter() | |
| .append('g') | |
| .attr('class', 'percent') | |
| .attr('transform', function(d) { return "translate(" + (xScale(d)) + ", 0)"; }); | |
| enter.append('text') | |
| .text(function(d) { return d; }) | |
| .attr('y', margin.top / 2) | |
| .attr('text-anchor', 'middle'); | |
| // Linear square side scale | |
| var rScale1 = d3.scale.linear() | |
| .domain([0, 100]) | |
| .range([0, maxSide]); | |
| enter.append("rect") | |
| .attr('x', function(d) { return -(rScale1(d) / 2); }) | |
| .attr('y', function(d) { return yScale(0) - (rScale1(d) / 2); }) | |
| .attr("width", function(d) { return rScale1(d); }) | |
| .attr("height", function(d) { return rScale1(d); }); | |
| // Linear square area scale | |
| var rScale2 = d3.scale.linear() | |
| .domain([Math.sqrt(0), Math.sqrt(100)]) | |
| .range([0, maxSide]); | |
| enter.append("rect") | |
| .attr('x', function(d) { return -(rScale2(Math.sqrt(d)) / 2); }) | |
| .attr('y', function(d) { return yScale(1) - (rScale2(Math.sqrt(d)) / 2); }) | |
| .attr("width", function(d) { return rScale2(Math.sqrt(d)); }) | |
| .attr("height", function(d) { return rScale2(Math.sqrt(d)); }); | |
| // Linear circle radius scale | |
| var rScale3 = d3.scale.linear() | |
| .domain([0, 100]) | |
| .range([0, maxRadius]); | |
| enter.append("circle") | |
| .attr("cy", function(d) { return yScale(2); }) | |
| .attr("r", function(d) { return rScale3(d); }); | |
| // Linear circle area scale | |
| var rScale4 = d3.scale.linear() | |
| .domain([Math.sqrt(0 / Math.PI), Math.sqrt(100 / Math.PI)]) | |
| .range([0, maxRadius]); | |
| enter.append("circle") | |
| .attr("cy", function(d) { return yScale(3); }) | |
| .attr("r", function(d) { return rScale4(Math.sqrt(d / Math.PI)); }); | |
| // Square root power scale | |
| var rScale5 = d3.scale.sqrt() | |
| .domain([0, 100]) | |
| .range([0, maxRadius]); | |
| enter.append("circle") | |
| .attr("cy", function(d) { return yScale(4); }) | |
| .attr("r", function(d) { return rScale5(d); }); | |
| </script> |
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