Ch. 12, Fig. 9 - D3.js in Action

This is the code for Chapter 12, Figure 9 from D3.js in Action which requires a touch interface (or emulator) to see any effect. This implements panning (single touch), pinch zooming (two-finger touch), and rotation (three-finger touch) simultaneously.

<html>
<head>
  <title>D3 in Action Chapter 12 - Example 8</title>
  <meta charset="utf-8" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js"></script>
</head>
<style>
  body, html {
    width:100%;
    height:100%;
  }
  #vizcontainer {
    width:100%;
    height:100%;
  }
  svg {
    width: 100%;
    height: 100%;
  }
</style>
<body>
<div id="vizcontainer">
  <svg></svg>
</div>
</body>
  <footer>
    
<script>
    var initialD = [];
    var initialTransform;

d3.select("svg").on("touchstart", touchBegin);
    d3.select("svg").on("touchend", touchBegin);
    d3.select("svg").on("touchmove", touchUpdate);

var touchColor = d3.scale.linear().domain([0, 10]).range(["pink", "darkred"])

var graphicsG = d3.select("svg").append("g").attr("id", "graphics")
    .attr("transform-origin", "250 250");

sampleData = d3.range(10).map(function(d) {
    var datapoint = {};
    datapoint.id = "Sample " + d;
    datapoint.x = Math.random() * 500;
    datapoint.y = Math.random() * 500;
    return datapoint;
  })
     
     var samples = graphicsG.selectAll("g")
     .data(sampleData)
     .enter()
     .append("g")
     .attr("transform", function(d) {return "translate("+d.x+","+d.y+")"});
     
     var sampleSubG = samples.append("g").attr("class", "sample");
     sampleSubG.append("rect").attr("width", 100).attr("height", 100)
     .style("fill", "red").style("stroke", "gray").style("stroke-width", "1px");

sampleSubG.append("text").text(function (d) {return d.id}).attr("y", 20);

function touchBegin() {
      d3.event.preventDefault();
      d3.event.stopPropagation();
       
      d = d3.touches(this);
      initialD = d;
      initialTransform = d3.transform(d3.select("#graphics").attr("transform"));

}
     function touchUpdate() {
       d3.event.preventDefault();
       d3.event.stopPropagation();
       d = d3.touches(this);
       d3.select("svg").selectAll("circle.fingertips").data(d).enter().append("circle")
       .attr("class", "fingertips").attr("r", 75).style("fill", function(d, i) {
         return touchColor(i)
       });

d3.select("svg").selectAll("circle.fingertips").data(d).exit().remove();

d3.select("svg").selectAll("circle.fingertips").attr("cx", function(d) {
         return d[0]
       }).attr("cy", function(d) {
         return d[1]
       });
       
        var newX = initialTransform.translate[0];
        var newY = initialTransform.translate[1];
        var newRotate = initialTransform.rotate;
        var newScale = initialTransform.scale[0];

d3.select("#touchStatus").html("")

if (d.length == 1) {
        newX = -(initialD[0][0] - d[0][0] - initialTransform.translate[0]);
        newY = -(initialD[0][1] - d[0][1] - initialTransform.translate[1]);
      }
      else if (d.length == 2) {
        d3.select("#touchStatus").append("p").html("Two Fingers");

var initialLength = Math.sqrt(Math.abs(initialD[0][0] - initialD[1][0]) + Math.abs(initialD[0][1] - initialD[1][1]));
        var currentLength = Math.sqrt(Math.abs(d[0][0] - d[1][0]) + Math.abs(d[0][1] - d[1][1]));
        var zoom = currentLength / initialLength;
        newScale = zoom * initialTransform.scale[0];
      }
      else if (d.length == 3) {
        var slope1 = (initialD[0][1] - initialD[1][1]) / (initialD[0][0] - initialD[1][0]);
        var slope2 = (d[0][1] - d[1][1]) / (d[0][0] - d[1][0]);
        
        var angle = Math.atan((slope1 - slope2)/(1 + slope1*slope2)) * 180/Math.PI;
        var newRotate = initialTransform.rotate - angle;

d3.selectAll("g.sample > text").attr("transform", "rotate(" +(-newRotate)+")")

}

d3.select("#touchStatus").append("p").html("New Scale: " + newScale);
      
      d3.select("#graphics").attr("transform", "translate(" +(newX) +"," + (newY) + ") scale("+newScale+") rotate(" + newRotate + ")")

}
</script>
  </footer>

</html>

https://cdnjs.cloudflare.com/ajax/libs/d3/3.5.5/d3.min.js