使用Ajax调用进行Highchart更新问题

Question

我遇到了ajax调用的更新高亮图问题。每当ajax调用运行时，它都会破坏整个饼图。

我的计划

$('#container').highcharts({
                chart: {
                    type: 'pie'
                },
                title: {
                    text: 'Browser market shares. January, 2015 to May, 2015'
                },
                subtitle: {
                    text: 'Click the slices to view versions. Source: netmarketshare.com.'
                },
                plotOptions: {
                    series: {
                        dataLabels: {
                            enabled: true,
                            format: '{point.name}: {point.y:.1f}%'
                        }
                    }
                },

                tooltip: {
                    headerFormat: '<span style="font-size:11px">{series.name}</span><br>',
                    pointFormat: '<span style="color:{point.color}">{point.name}</span>: <b>{point.y:.2f}%</b> of total<br/>'
                },
                series: [{
                    name: 'Brands',
                    colorByPoint: true,
                    data: [<?php echo $cok; ?>]
                }]
            });

$cok变量的值为{ name: 'No Answer', y: 10, drilldown: 'No Answer' },{ name: 'No Answer', y: 20, drilldown: 'No Answer' }。但是当我使用ajax调用在Piechart中更新这些值时，它会破坏整个饼图。

我的Ajax电话：

setInterval(function(){
$.ajax({
                 type: "POST",
                 url: 'callexport.php',
                 data: {pie_ajax_campaign:'<?php echo $_SESSION['scampaign']; ?>',pie_ajax_date:$("#daterange").val() },
                 cache: false,
                 success: function(piedata)
                 {
                    $('#container').highcharts({
                chart: {
                    type: 'pie'
                },
                title: {
                    text: 'Browser market shares. January, 2015 to May, 2015'
                },
                subtitle: {
                    text: 'Click the slices to view versions. Source: netmarketshare.com.'
                },
                plotOptions: {
                    series: {
                        dataLabels: {
                            enabled: true,
                            format: '{point.name}: {point.y:.1f}%'
                        }
                    }
                },

                tooltip: {
                    headerFormat: '<span style="font-size:11px">{series.name}</span><br>',
                    pointFormat: '<span style="color:{point.color}">{point.name}</span>: <b>{point.y:.2f}%</b> of total<br/>'
                },
                series: [{
                    name: 'Brands',
                    colorByPoint: true,
                    data: [piedata]
                }]
            });
                    return false;
                }});


            },20000);