script.js

var a2 = Math.atan2(source.y, source.x);
var a1 = Math.atan2(compare.y, compare.x);
var sign = a1 > a2 ? 1 : -1;
var angle = a1 - a2;
var K = -sign * Math.PI * 2;
var angle = (Math.abs(K + angle) < Math.abs(angle))? K + angle : angle;

var jsonCircles = [
  { "x_axis": 30, "y_axis": 30, "radius": 20, "color" : "green" },
  { "x_axis": 70, "y_axis": 70, "radius": 20, "color" : "purple"},
  { "x_axis": 110, "y_axis": 100, "radius": 20, "color" : "red"}];

var svgContainer = d3.select("body").append("svg")
                                    .attr("width", 200)
                                    .attr("height", 200);

var circles = svgContainer.selectAll("circle")
                          .data(jsonCircles)
                          .enter()
                          .append("circle");

var circleAttributes = circles
                       .attr("cx", function (d) { return d.x_axis; })
                       .attr("cy", function (d) { return d.y_axis; })
                       .attr("r", function (d) { return d.radius; })
                       .style("fill", function(d) { return d.color; });