Ro4052/.block

## .block
license: mit

## README.md

      
    Raw
  

              README.md
            
          
    In this block, I will demonstrate a way to draw a colour range legend using D3FC components. You can also read my blog post where I describe how I went about developing the legend https://blog.scottlogic.com/2019/03/13/how-to-create-a-continuous-colour-range-legend-using-d3-and-d3fc.

  
## index.html
<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://unpkg.com/d3@5.7.0/dist/d3.min.js"></script>
  <script src="https://unpkg.com/d3fc@14.0.27/build/d3fc.js"></script>
  <style>

    body {
      margin: 0;
      top: 0;
      right: 0;
      bottom: 0;
      left: 0;
    }

  </style>
</head>

<body>
  <div id="chart"></div>
  <script>

    const container = d3.select("#chart");
    const colourScale = d3
    	.scaleSequential(d3.interpolateViridis)
    	.domain([0, 22]);
    const domain = colourScale.domain();

    const width = 100;
    const height = 150;

    const paddedDomain = fc.extentLinear()
  		.pad([0.1, 0.1])
  		.padUnit("percent")(domain);
		const [min, max] = paddedDomain;
		const expandedDomain = d3.range(min, max, (max - min) / height);

    const xScale = d3
    	.scaleBand()
    	.domain([0, 1])
    	.range([0, width]);

    const yScale = d3
    	.scaleLinear()
    	.domain(paddedDomain)
    	.range([height, 0]);

    const svgBar = fc
      .autoBandwidth(fc.seriesSvgBar())
      .xScale(xScale)
      .yScale(yScale)
      .crossValue(0)
      .baseValue((_, i) => (i > 0 ? expandedDomain[i - 1] : 0))
      .mainValue(d => d)
      .decorate(selection => {
        selection.selectAll("path").style("fill", d => colourScale(d));
      });

    const axisLabel = fc
      .axisRight(yScale)
      .tickValues([...domain, (domain[1] + domain[0]) / 2])
      .tickSizeOuter(0);

    const legendSvg = container.append("svg")
    	.attr("height", height)
    	.attr("width", width);

    const legendBar = legendSvg
    	.append("g")
    	.datum(expandedDomain)
    	.call(svgBar);

    const barWidth = Math.abs(legendBar.node().getBoundingClientRect().x);
    legendSvg.append("g")
    	.attr("transform", `translate(${barWidth})`)
      .datum(expandedDomain)
      .call(axisLabel)
      .select(".domain")
      .attr("visibility", "hidden");

    container.style("margin", "1em");

  </script>
</body>
	<!DOCTYPE html>
	<head>
	<meta charset="utf-8">
	<script src="https://unpkg.com/d3@5.7.0/dist/d3.min.js"></script>
	<script src="https://unpkg.com/d3fc@14.0.27/build/d3fc.js"></script>
	<style>

	body {
	margin: 0;
	top: 0;
	right: 0;
	bottom: 0;
	left: 0;
	}

	</style>
	</head>

	<body>
	<div id="chart"></div>
	<script>

	const container = d3.select("#chart");
	const colourScale = d3
	.scaleSequential(d3.interpolateViridis)
	.domain([0, 22]);
	const domain = colourScale.domain();

	const width = 100;
	const height = 150;

	const paddedDomain = fc.extentLinear()
	.pad([0.1, 0.1])
	.padUnit("percent")(domain);
	const [min, max] = paddedDomain;
	const expandedDomain = d3.range(min, max, (max - min) / height);

	const xScale = d3
	.scaleBand()
	.domain([0, 1])
	.range([0, width]);

	const yScale = d3
	.scaleLinear()
	.domain(paddedDomain)
	.range([height, 0]);

	const svgBar = fc
	.autoBandwidth(fc.seriesSvgBar())
	.xScale(xScale)
	.yScale(yScale)
	.crossValue(0)
	.baseValue((_, i) => (i > 0 ? expandedDomain[i - 1] : 0))
	.mainValue(d => d)
	.decorate(selection => {
	selection.selectAll("path").style("fill", d => colourScale(d));
	});

	const axisLabel = fc
	.axisRight(yScale)
	.tickValues([...domain, (domain[1] + domain[0]) / 2])
	.tickSizeOuter(0);

	const legendSvg = container.append("svg")
	.attr("height", height)
	.attr("width", width);

	const legendBar = legendSvg
	.append("g")
	.datum(expandedDomain)
	.call(svgBar);

	const barWidth = Math.abs(legendBar.node().getBoundingClientRect().x);
	legendSvg.append("g")
	.attr("transform", `translate(${barWidth})`)
	.datum(expandedDomain)
	.call(axisLabel)
	.select(".domain")
	.attr("visibility", "hidden");

	container.style("margin", "1em");

	</script>
	</body>