Visualforce Charting with drill down when clicking on chart sections/bars

VisualforceDrilldownChart.page

<apex:chart height="300" width="300" data="{!data}”>
    <apex:axis type="Category" position="bottom" fields="ctype">
        <apex:chartLabel rotate="270"/>
    </apex:axis>
    <apex:axis type="Numeric" position="left" fields="cval"/>
    <apex:barSeries axis="left" orientation="vertical" xField="ctype" yField="cval">
        <apex:chartTips rendererFn="renderer"/>
    </apex:barSeries>
</apex:chart>

<script type="text/javascript">
function renderer(klass, item) {
    var type = item.storeItem.get('ctype');
    var val = item.storeItem.get('cval');
    var e = window.event;
    var t = e.target || e.srcElement;
    t.onclick=function(event){
        window.parent.location = "{!$Page.MyDrilldown}?type="+type;
    };
    this.setTitle(type + " : " + val);
}
</script>