Linking pie chart with column chart for drill-down data display

HTML

<script type="text/javascript" src="http://www.amcharts.com/lib/3/amcharts.js"></script>
<script type="text/javascript" src="http://www.amcharts.com/lib/3/pie.js"></script>
<script type="text/javascript" src="http://www.amcharts.com/lib/3/serial.js"></script>
<div id="chartdiv1"></div>
<div id="chartdiv2"></div>

CSS

body {
    font-family: Verdana;
    font-size: 12px;
    padding: 10px;
}
#chartdiv1 {
    width : 49%;
    height : 300px;
    font-size : 11px;
    float: left;
}
#chartdiv2 {
    width : 50%;
    height : 300px;
    font-size : 11px;
    float: left;
}

JavaScript

var chartData = [{
    "department": "Marketing",
    "projects": 23,
    "url":"#",
    "description":"click to drill-down",
    "months": [
        { "category": 1, "projects": 1 },
        { "category": 2, "projects": 2 },
        { "category": 3, "projects": 1 },
        { "category": 4, "projects": 3 },
        { "category": 5, "projects": 2 },
        { "category": 6, "projects": 1 },
        { "category": 7, "projects": 2 },
        { "category": 8, "projects": 3 },
        { "category": 9, "projects": 3 },
        { "category": 10, "projects": 1 },
        { "category": 11, "projects": 1 },
        { "category": 12, "projects": 3 }
    ]
}, {
    "department": "Sales",
    "projects": 26,
    "url":"#",
    "description":"click to drill-down",
    "months": [
        { "category": 1, "projects": 4 },
        { "category": 2, "projects": 3 },
        { "category": 3, "projects": 1 },
        { "category": 4, "projects": 4 },
        { "category": 5, "projects": 2 },
        { "category": 6, "projects": 1 },
        { "category": 7, "projects": 2 },
        { "category": 8, "projects": 2 },
        { "category": 9, "projects": 3 },
        { "category": 10, "projects": 1 },
        { "category": 11, "projects": 1 },
        { "category": 12, "projects": 3 }
    ]
}, {
    "department": "Logistics",
    "projects": 30,
    "url":"#",
    "description":"click to drill-down",
    "months": [
        { "category": 1, "projects": 2 },
        { "category": 2, "projects": 3 },
        { "category": 3, "projects": 1 },
        { "category": 4, "projects": 5 },
        { "category": 5, "projects": 2 },
        { "category": 6, "projects": 1 },
        { "category": 7, "projects": 2 },
        { "category": 8, "projects": 2 },
        { "category": 9, "projects": 3 },
        { "category": 10, "projects": 1 },
        { "category": 11, "projects": 1 },
        { "category": 12, "projects": 3 }
    ]
}];

// aggregate collective data
var collectiveData = [];
for (var...