Google Visualization - 错误类型不匹配

Question

我的折线图一直收到以下错误 - 几天前工作正常，但现在我收到以下错误...

错误：类型不匹配。值0与列索引1中的类型编号不匹配  我的图表代码如下......

这表明我添加到第一列的移位值不会被识别为数字，但我不明白为什么？

drawDisplacementChart(xml, markers){
          //array to hold data
          var graph = [];

          //data table object
          var dataTable = new google.visualization.DataTable();

          //chart options
          var options = {title:'Displacement (m)/Time (minutes)', 
                  legend:{position:'bottom'},
                  is3d:true     
              };

              //get first point of route- displacement is distance travelled away from this point
              var startPoint = new google.maps.LatLng(markers[0].getAttribute("lat"),markers[0].getAttribute("lng"));

              //loop through xml
              for(var i = 0; i<markers.length; i++){
                  //var to represent time - reading being taken every minute
                  var time = i+':00';
                  //find the current position in route
                  var current = new google.maps.LatLng(markers[i].getAttribute("lat"),markers[i].getAttribute("lng"));
                  //calculate displacement
                  var displacement = google.maps.geometry.spherical.computeDistanceBetween(startPoint,current);
                  console.log(displacement);
                  //store values in array
                  graph[i] = [time, displacement];
              }

              //instantiates chart object
              var chart = new google.visualization.LineChart(document.getElementById('chart_div2'));
              //set columns in data table
              dataTable.addColumn('string', 'time');
              dataTable.addColumn('number', 'Displacement');


              var array = [];
              //loop through stored values
              for(var i = 0; i<graph.length; i++){
                  //timeout to allow periodic addition
                       setTimeout(function(y){
                        array.push(graph[y]);
                        dataTable.addRows(array); 
                        //add value to chart
                        chart.draw(dataTable, options); 
                        //empty array for next iteration
                        array = [];
                  }, i*TIME, i);
              }

      }