d3 - Condegram Spiral Plot

d3.js v4 Condegram Spiral Plot like the one pictured here. Coded to answer this StackOverflow question

<!DOCTYPE html>
<html>

<body>
  <div id="chart"></div>
  <script>
    var width = 500,
      height = 500,
      start = 0,
      end = 2.25,
      numSpirals = 4;

var theta = function(r) {
      return numSpirals * Math.PI * r;
    };

var r = d3.min([width, height]) / 2 - 40;

var radius = d3.scaleLinear()
      .domain([start, end])
      .range([40, r]);

var svg = d3.select("#chart").append("svg")
      .attr("width", width)
      .attr("height", height)
      .append("g")
      .attr("transform", "translate(" + width / 2 + "," + height / 2 + ")");

// create the spiral, borrowed from https://bl.ocks.org/syntagmatic/3543186
    var points = d3.range(start, end + 0.001, (end - start) / 1000);

var spiral = d3.radialLine()
      .curve(d3.curveCardinal)
      .angle(theta)
      .radius(radius);

var path = svg.append("path")
      .datum(points)
      .attr("id", "spiral")
      .attr("d", spiral)
      .style("fill", "none")
      .style("stroke", "steelblue");

// fudge some data, 2 years of data starting today
    var spiralLength = path.node().getTotalLength(),
        N = 730,
        barWidth = (spiralLength / N) - 1;
    var someData = [];
    for (var i = 0; i < N; i++) {
      var currentDate = new Date();
      currentDate.setDate(currentDate.getDate() + i);
      someData.push({
        date: currentDate,
        value: Math.random()
      });
    }
    
    // here's our time scale that'll run along the spiral
    var timeScale = d3.scaleTime()
      .domain(d3.extent(someData, function(d){
        return d.date;
      }))
      .range([0, spiralLength]);
    
    // yScale for the bar height
    var yScale = d3.scaleLinear()
      .domain([0, d3.max(someData, function(d){
        return d.value;
      })])
      .range([0, (r / numSpirals) - 30]);

// append our rects
    svg.selectAll("rect")
      .data(someData)
      .enter()
      .append("rect")
      .attr("x", function(d,i){
        
        // placement calculations
        var linePer = timeScale(d.date),
            posOnLine = path.node().getPointAtLength(linePer),
            angleOnLine = path.node().getPointAtLength(linePer - barWidth);
      
        d.linePer = linePer; // % distance are on the spiral
        d.x = posOnLine.x; // x postion on the spiral
        d.y = posOnLine.y; // y position on the spiral
        
        d.a = (Math.atan2(angleOnLine.y, angleOnLine.x) * 180 / Math.PI) - 90; //angle at the spiral position

return d.x;
      })
      .attr("y", function(d){
        return d.y;
      })
      .attr("width", function(d){
        return barWidth;
      })
      .attr("height", function(d){
        return yScale(d.value);
      })
      .style("fill", "steelblue")
      .style("stroke", "none")
      .attr("transform", function(d){
        return "rotate(" + d.a + "," + d.x  + "," + d.y + ")"; // rotate the bar
      });
    
    // add date labels
    var tF = d3.timeFormat("%b %Y"),
        firstInMonth = {};
    svg.selectAll("text")
      .data(someData)
      .enter()
      .append("text")
      .attr("dy", 10)
      .style("text-anchor", "start")
      .style("font", "10px arial")
      .append("textPath")
      // only add for the first of each month
      .filter(function(d){
        var sd = tF(d.date);
        if (!firstInMonth[sd]){
          firstInMonth[sd] = 1;
          return true;
        }
        return false;
      })
      .text(function(d){
        return tF(d.date);
      })
      // place text along spiral
      .attr("xlink:href", "#spiral")
      .style("fill", "grey")
      .attr("startOffset", function(d){
        return ((d.linePer / spiralLength) * 100) + "%";
      })

</script>
</body>

</html>
 Run code snippetCopy snippet to answer

https://d3js.org/d3.v4.js