amcharts Bubble simple

HTML

<script src="http://www.amcharts.com/lib/amcharts.js" type="text/javascript"></script>
<div id="chartdiv" style="width: 100%; height: 362px;"></div>

JavaScript

var chart;

var chartData = [{
    x: 10,
    y: 14,
    value: 59},
{
    x: 5,
    y: 3,
    value: 50},
{
    x: -10,
    y: -3,
    value: 19},
{
    x: -6,
    y: 5,
    value: 65},
{
    x: 15,
    y: -4,
    value: 92},
{
    x: 13,
    y: 1,
    value: 8},
{
    x: 1,
    y: 6,
    value: 35}];

AmCharts.ready(function() {
    // XY Chart
    chart = new AmCharts.AmXYChart();
    chart.pathToImages = "http://www.amcharts.com/lib/images/";
    chart.marginRight = 0;
    chart.marginTop = 0;    
    chart.autoMarginOffset = 0;    
    chart.dataProvider = chartData;
    chart.startDuration = 1.5;

    // AXES
    // X
    var xAxis = new AmCharts.ValueAxis();
    xAxis.title = "X Axis";
    xAxis.position = "bottom";
    xAxis.axisColor = "#DADADA"    
    xAxis.autoGridCount = true;
    chart.addValueAxis(xAxis);

    // Y
    var yAxis = new AmCharts.ValueAxis();
    yAxis.title = "Y Axis";
    yAxis.position = "left";
    yAxis.axisColor = "#DADADA"
    yAxis.autoGridCount = true;
    chart.addValueAxis(yAxis);

    // GRAPH
    var graph = new AmCharts.AmGraph();
    graph.valueField = "value"; // valueField responsible for the size of a bullet
    graph.xField = "x";
    graph.yField = "y";
    graph.lineAlpha = 0;
    graph.bullet = "bubble";
    chart.addGraph(graph);
    
    // SCROLLBAR
    var chartScrollbar = new AmCharts.ChartScrollbar();
    chart.addChartScrollbar(chartScrollbar);    

    // WRITE                                
    chart.write("chartdiv");
});