使用谷歌图表

Question

这是我的HTML代码：

google.load('visualization', '1', {'packages':['Table']});

// Set a callback to run when the Google Visualization API is loaded.
google.setOnLoadCallback(drawChart);

function drawChart() {
  var jsonData = $.ajax({
      url: "http://localhost:8080/getData.php",
      dataType:"json",
      async: false
      }).responseText;

  var myArr = $.parseJSON(jsonData);
  // Create our data table out of JSON data loaded from server.
  var data = new google.visualization.DataTable(myArr);
    data.addRows(myArr.length);
    data.addColumn('string','emp_name');
    data.addColumn('string','works_on');
    data.addColumn('datetime','time_from');
    data.addColumn('datetime','time_to');
    data.addColumn('number','Number of Hours');

  $.each(myArr, function(i,d) {
    data.setValue(i,0,d.emp_name);
    data.setValue(i,1,d.works_on);
    data.setValue(i,2,new Date(d.time_from));
    data.setValue(i,3,new Date(d.time_to));
  });

var formatter3 = new google.visualization.DateFormat({pattern: "d-MM-yyyyTHH:mm:SS"});
formatter3.format(data,2);
formatter3.format(data,3);

  // Instantiate and draw our chart, passing in some options.
  var chart = new google.visualization.Table(document.getElementById('chart_div'));
  chart.draw(data,null);

}

我想通过计算每个员工的总工作时间绘制一个饼图（例如：＆＃34; ABC-10hr，xyz-5hr＆＃34;等等）。到目前为止，我已经完成了这么多工作并请帮助我在策划部分。