stock Programatically force grouping into periods

HTML

<script src="http://www.amcharts.com/lib/amstock.js" type="text/javascript"></script>
<div id="chartdiv" style="width: 100%; height: 370px;"></div>

Group to:
<input type="button" value="Days" onclick="group('DD')" />
<input type="button" value="Weeks" onclick="group('WW')" />
<input type="button" value="Months" onclick="group('MM')" />

CSS

body
{
    font-size:12px;
    color:#000000;
    background-color:#ffffff;
    font-family:verdana,helvetica,arial,sans-serif;
}

.amChartsButtonSelected
{
   background-color:#CC0000;
   border-style:solid;
   border-color:#CC0000;
   border-width:1px;
   color:#FFFFFF;
  -moz-border-radius: 5px;
  border-radius: 5px;
  margin: 1px;   
    padding:3px;
}

.amChartsButton
{
   background-color:#EEEEEE;
   border-style:solid;
   border-color:#CCCCCC;
   border-width:1px;
   color:#000000;
  -moz-border-radius: 5px;
  border-radius: 5px;
  margin: 1px; 
    padding:3px;
}

.amChartsCompareList
{
   border-style:solid;
   border-color:#CCCCCC;
   border-width:1px;
}

JavaScript

var chart;
var chartData = [];
var newPanel;
var stockPanel;

function generateChartData() {
    var firstDate = new Date();
    firstDate.setHours(0, 0, 0, 0);
    firstDate.setDate(firstDate.getDate() - 2000);

    for (var i = 0; i < 2000; i++) {
        var newDate = new Date(firstDate);

        newDate.setDate(newDate.getDate() + i);

        var open = Math.round(Math.random() * (30) + 100);
        var close = open + Math.round(Math.random() * (15) - Math.random() * 10);

        var low
        if (open < close) {
            low = open - Math.round(Math.random() * 5);
        }
        else {
            low = close - Math.round(Math.random() * 5);
        }

        var high;
        if (open < close) {
            high = close + Math.round(Math.random() * 5);
        }
        else {
            high = open + Math.round(Math.random() * 5);
        }

        var volume = Math.round(Math.random() * (1000 + i)) + 100 + i;

        var value = Math.round(Math.random() * (30) + 100);

        chartData[i] = ({
            date: newDate,
            open: open,
            close: close,
            high: high,
            low: low,
            volume: volume,
            value: value
        });
    }
}
    
AmCharts.ready(function() {
    generateChartData();
    createStockChart();
});    

function createStockChart() {
    chart = new AmCharts.AmStockChart();
    chart.pathToImages = "http://www.amcharts.com/lib/images/";

    // DATASET //////////////////////////////////////////
    var dataSet = new AmCharts.DataSet();
    dataSet.fieldMappings = [{
        fromField: "open",
        toField: "open"},
    {
        fromField: "close",
        toField: "close"},
    {
        fromField: "high",
        toField: "high"},
    {
        fromField: "low",
        toField: "low"},
    {
        fromField: "volume",
        toField: "volume"},
    {
        fromField: "value",
        toField: "value"}];
    dataSet.color = "#7f8da9";
   ...