title: TypeError: google.visualization.DataTable is not a constructor
body: <p>On my web page I have a google map, as well as three charts. When the page loads the map is fine, but the charts either don't load or only one or two do. Keep getting the error TypeError: google.visualization.DataTable is not a constructor.   </p>
  
  <pre><code>function load() {
       //map object
          var MY_MAP = new google.maps.Map(document.getElementById("map"), {
          center: {lat: 54.870902, lng: -6.300565}, 
          zoom: 14
        });    
        //call to get and process data
        downloadUrl("Map.php", processXML);
    }  
  
   // Load the Visualization API and the piechart package.
        google.load('visualization', '1.0', {'packages':['corechart']}); 
          // Set a callback to run when the Google Visualization API is loaded. 
  google.setOnLoadCallback(drawAltitudeChart());  
  google.setOnLoadCallback(drawDisplacementChart());
  google.setOnLoadCallback(drawDistanceChart());  
  
  
  
  function drawAltitudeChart(){
  
           //console.log('hello');
           var graph = [];
            downloadUrl("Map.php", function (data){
                var xml = data.responseXML;
                var markers = xml.documentElement.getElementsByTagName("marker");
                var dataTable = new google.visualization.DataTable();
                var options = {title:'Altitude (m above sea level)', 
                    curveType:'function', 
                    legend:{position:'bottom'},
                    is3d:true     
                };
                var chart;
  
                for(var i = 0; i&lt;markers.length; i++){
                    graph[i] = ['', parseInt(markers[i].getAttribute("alt"))];   
                }
  
                dataTable.addColumn('string', 'id');
                dataTable.addColumn('number', 'Altitude');
                dataTable.addRows(graph);
  
  
                chart = new google.visualization.LineChart(document.getElementById('curve_chart'));
                chart.draw(dataTable, options); 
  
            });
        }  
  </code></pre>