1 // Ratio of Obese (BMI >= 30) in U.S. Adults, CDC 2008

     2 var data = [

     3   , .187, .198, , .133, .175, .151, , .1, .125, .171, , .172, .133, , .108,

     4   .142, .167, .201, .175, .159, .169, .177, .141, .163, .117, .182, .153, .195,

     5   .189, .134, .163, .133, .151, .145, .13, .139, .169, .164, .175, .135, .152,

     6   .169, , .132, .167, .139, .184, .159, .14, .146, .157, , .139, .183, .16, .143

     7 ];

     8 

     9 var color = d3.scale.linear()

    10     .domain([d3.min(data), d3.max(data)])

    11     .range(["#aad", "#556"]); 

    12 

    13 var force = d3.layout.force()

    14     .charge(0)

    15     .gravity(0)

    16     .size([960, 500]);

    17 

    18 var svg = d3.select("#chart").append("svg:svg")

    19     .attr("width", 960 + 100)

    20     .attr("height", 500 + 100)

    21   .append("svg:g")

    22     .attr("transform", "translate(50,50)");

    23 

    24 d3.json("../data/us-state-centroids.json", function(states) {

    25   var project = d3.geo.albersUsa(),

    26       idToNode = {},

    27       links = [],

    28       nodes = states.features.map(function(d) {

    29     var xy = project(d.geometry.coordinates);

    30     return idToNode[d.id] = {

    31       x: xy[0],

    32       y: xy[1],

    33       gravity: {x: xy[0], y: xy[1]},

    34       r: Math.sqrt(data[+d.id] * 5000),

    35       value: data[+d.id]

    36     };

    37   });

    38 

    39   force

    40       .nodes(nodes)

    41       .links(links)

    42       .start()

    43       .on("tick", function(e) {

    44     var k = e.alpha,

    45         kg = k * .02;

    46     nodes.forEach(function(a, i) {

    47       // Apply gravity forces.

    48       a.x += (a.gravity.x - a.x) * kg;

    49       a.y += (a.gravity.y - a.y) * kg;

    50       nodes.slice(i + 1).forEach(function(b) {

    51         // Check for collisions.

    52         var dx = a.x - b.x,

    53             dy = a.y - b.y,

    54             l = Math.sqrt(dx * dx + dy * dy),

    55             d = a.r + b.r;

    56         if (l < d) {

    57           l = (l - d) / l * k;

    58           dx *= l;

    59           dy *= l;

    60           a.x -= dx;

    61           a.y -= dy;

    62           b.x += dx;

    63           b.y += dy;

    64         }

    65       });

    66     });

    67 

    68     svg.selectAll("circle")

    69         .attr("cx", function(d) { return d.x; })

    70         .attr("cy", function(d) { return d.y; });

    71   });

    72 

    73   svg.selectAll("circle")

    74       .data(nodes)

    75     .enter().append("svg:circle")

    76       .style("fill", function(d) { return color(d.value); })

    77       .attr("cx", function(d) { return d.x; })

    78       .attr("cy", function(d) { return d.y; })

    79       .attr("r", function(d, i) { return d.r; });

    80 });