D3 Examples - Color Scale

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<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <script src="https://d3js.org/d3.v5.min.js"></script>
</head>
​
<body>
  <script>
    var margin = {left: 20, top: 20, right: 40, bottom: 20},
        width = 950 - margin.left - margin.right,
        height = 500 - margin.top - margin.bottom;
    var svg = d3.select("body").append("svg")
      .attr("width", width + margin.left + margin.right)
      .attr("height", height + margin.top + margin.bottom)
        .append('g')
        .attr('transform', 'translate(' + [margin.left, margin.top] + ')');
    console.log('width', width)
    var data = [];
    for (var i=0; i<40; i++) { data.push(i) }
    
    var x = d3.scalePoint() 
            .range([0,width])
            .domain(data.map(d => d))
            .padding(0.05);
    
    var rainbow = d3.scaleSequential(d3.interpolatePiYG)
            .domain(d3.extent(data,d=>d));
    
    svg.selectAll('rect')
        .data(data)
        .enter().append('rect')
        .attr('x', d => x(d))
        .attr('y', height/2 - 50)
        .attr('width', x.step())
        .attr('height', 100)
        .attr('fill', d => rainbow(d))
​
  </script>
</body>
​
    