Switching chart type on the fly between Serial and Pie

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/serial.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/themes/none.js"></script>
<div class="type-selector">
    Select chart type:
    <label><input type="radio" name="type" value="line" onclick="setType(this.value);" checked="checked" /> Line</label>
    <label><input type="radio" name="type" value="area" onclick="setType(this.value);" /> Area</label>
    <label><input type="radio" name="type" value="column" onclick="setType(this.value);" /> Column</label>
    <label><input type="radio" name="type" value="pie" onclick="setType(this.value);" /> Pie</label>
</div>
<div id="chartdiv" class="chartdiv" style="display: block;"></div>
<div id="chartdiv2" class="chartdiv" style="display: none;"></div>

CSS

body {
    font-family: Verdana;
}

.chartdiv {
	width		: 100%;
	height		: 300px;
	font-size	: 11px;
}

.type-selector {
    padding: 10px;
    background: #ddd;
}

.type-selector label {
    margin: 0px 10px;
    cursor: pointer;
}

JavaScript

// set chart data
var chartData = [{
    "country": "USA",
    "visits": 2025
}, {
    "country": "China",
    "visits": 1882
}, {
    "country": "Japan",
    "visits": 1809
}, {
    "country": "Germany",
    "visits": 1322
}, {
    "country": "UK",
    "visits": 1122
}, {
    "country": "France",
    "visits": 1114
}, {
    "country": "India",
    "visits": 984
}];

// create serial chart
var chart = AmCharts.makeChart("chartdiv", {
    "type": "serial",
    "dataProvider": chartData,
    "startDuration": 1,
    "valueAxes": [{
        "gridColor":"#FFFFFF",
		"gridAlpha": 0.2,
		"dashLength": 0
    }],
    "gridAboveGraphs": true,
    "startDuration": 1,
    "graphs": [{
        "lineAlpha": 1,
        "lineThickness": 2,
        "type": "line",
        "valueField": "visits"		
    }],
    "categoryField": "country"
});

// create pie chart
var chart2 = AmCharts.makeChart("chartdiv2", {
    "type": "pie",
    "dataProvider": chartData,
    "startDuration": 1,
    "valueField": "visits",
    "titleField": "country"
});

function setType (type) {
    switch(type) {
        case 'line':
            chart.graphs[0].type = 'line';
            chart.graphs[0].lineAlpha = 1;
            chart.graphs[0].fillAlphas = 0;
            chart.validateNow();
            break;
        case 'area':
            chart.graphs[0].type = 'line';
            chart.graphs[0].lineAlpha = 1;
            chart.graphs[0].fillAlphas = 0.3;
            chart.validateNow();
            break;
        case 'column':
            chart.graphs[0].type = 'column';
            chart.graphs[0].lineAlpha = 0;
            chart.graphs[0].fillAlphas = 0.5;
            chart.validateNow();
            break;
       case 'pie':
            document.getElementById('chartdiv').style.display = 'none';
            document.getElementById('chartdiv2').style.display = 'block';
            chart2.invalidateSize();
            chart2.animateAgain();
            return;
    }
    
   ...