Edit in JSFiddle

// Variables
var skeleton; // Storing the skeleton data
var positions; // Storing the joint positions
var positions_scaled; // Storing the scaled joint positions
var figureScale = 2; // The scaling factor for our visualizations
var h = 200; // The height of the visualization
var w = 400; // The width of the visualization
var gap = 40;
var skip = 4;

function draw() {
  var parent = d3.select("body").select("#container");

  var svg = parent.append("svg")
    .attr("width", w)
    .attr("height", h)
    .attr("overflow", "scroll")
    .style("display", "inline-block");

  // Scale the data
  positions_scaled = positions.map(function(f, j) {
    return f.map(function(d, i) {
      return {
        x: (d.x + 50) * figureScale,
        y: -1 * d.y * figureScale + h - 10,
        z: d.z * figureScale
      };
    });
  });

  // Choose the frame to draw
  index = 60; // the index of the frame
  currentFrame = positions_scaled[index];

  headJoint = 7;

  svg.selectAll("circle.joints" + index)
    .data(currentFrame)
    .enter()
    .append("circle")
    .attr("cx", function(d) {
      return d.x;
    }).attr("cy", function(d) {
      return d.y;
    }).attr("r", function(d, i) {
      if (i == headJoint)
        return 4;
      else
        return 2;
    }).attr("fill", function(d, i) {
      return '#555555';
    });

  // Bones
  svg.selectAll("line.bones" + index)
    .data(skeleton)
    .enter()
    .append("line")
    .attr("stroke", "#555555")
    .attr("stroke-width", 1)
    .attr("x1", 0).attr("x2", 0)
    .attr("x1", function(d, j) {
      return currentFrame[d[0]].x;
    })
    .attr("x2", function(d, j) {
      return currentFrame[d[1]].x;
    })
    .attr("y1", function(d, j) {
      return currentFrame[d[0]].y;
    })
    .attr("y2", function(d, j) {
      return currentFrame[d[1]].y;
    });
}

// Read the files
$.getJSON("http://omid.al/d3-mocap-demo/Skeleton_BEA.json", function(json1) {
  skeleton = json1;
  $.getJSON("http://omid.al/d3-mocap-demo/BEA1.json", function(json2) {
    positions = json2;
    draw();
  });
});