D3 Examples - D3 Fundamentals - Colouring Bar Chart

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<!DOCTYPE html>
<head>
  <meta charset="utf-8">
  <title>Drawing SVG Shapes with D3</title>
  <script src="https://d3js.org/d3.v4.min.js"></script>
  <style>
    body { margin:0;position:fixed;top:0;right:0;bottom:0;left:0; }
  </style>
</head>
​
<body>
  <script>
    var w = 300;
    var h = 100;
    var padding = 2;
    var dataset = [5, 10, 14, 20, 25];
    
    var svg = d3.select("body").append("svg")
                            .attr("width", w)
                            .attr("height", h);
    
    // function to add a specific color/KPI indicator
    function colorPicker(v){                    // v as value
        if(v <= 20) { return "#666666" }
      else if (v > 20) { return "#FF0033"}
    }
    
    // Build bar chart
    svg.selectAll("rect")                           // Take all the rect and create new ones
        .data(dataset)                                  // for all the diff elements in dataset
        .enter()                                                // If there aren't any on the page, create them
      .append("rect")                                   // Append rect
            .attr("x", function(d, i) {return i * (w / dataset.length);})
        .attr("y", function(d) { return h - (d * 4); })
            .attr("width", w / dataset.length - padding)
            .attr("height", function(d) { return d * 4; })
        // Colour using data
            .attr("fill", function(d) { return "rgb(0, 0," + (d * 10) + ")";})
        // Colour using the function above
            .attr("fill", function(d) { return colorPicker(d); })
​
  </script>
</body>
​
    