Padding line graph with empty values at the end and start

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/themes/none.js"></script>
<div id="chartdiv"></div>

CSS

#chartdiv {
	width	: 100%;
	height	: 500px;
}

JavaScript

var chart = AmCharts.makeChart("chartdiv", {
        "type": "serial",
        "theme": "none",
        "pathToImages": "http://www.amcharts.com/lib/3/images/",
        "dataDateFormat": "YYYY-MM-DD",
        "valueAxes": [{
            "id":"v1",
            "axisAlpha": 0,
            "position": "left"
        }],
        "graphs": [{
			"id": "g1",
            "bullet": "round",
            "bulletBorderAlpha": 1,
            "bulletColor": "#FFFFFF",
            "bulletSize": 5,
            "hideBulletsCount": 50,
            "lineThickness": 2,
            "title": "red line",
            "useLineColorForBulletBorder": true,
            "valueField": "value"
        }],
        "chartScrollbar": {
			"graph": "g1",
			"scrollbarHeight": 30
		},
        "chartCursor": {
            "cursorPosition": "mouse",
            "pan": true,
             "valueLineEnabled":true,
             "valueLineBalloonEnabled":true
        },
        "categoryField": "date",
        "categoryAxis": {
            "parseDates": true,
            "dashLength": 1,
            "minorGridEnabled": true,
            "position": "top"
        },
        exportConfig:{
          menuRight: '20px',
          menuBottom: '150px',
          menuItems: [{
          icon: 'http://www.amcharts.com/lib/3/images/export.png',
          format: 'png'	  
          }]  
        },
        "dataProvider": [{
            "date": "2012-07-26"
        }, {
            "date": "2012-08-26",
            "value": 11
        }, {
            "date": "2012-08-27",
            "value": 13
        }, {
            "date": "2012-08-28",
            "value": 18
        }, {
            "date": "2012-08-29",
            "value": 20
        }, {
            "date": "2012-08-30",
            "value": 29
        }, {
            "date": "2012-08-31",
            "value": 33
        }, {
            "date": "2012-09-01",
            "value": 42
        }, {
            "date": "2012-09-02",
            "value": 35
...