title: Google chart - All series on a given axis must be of the same data type
body: <p>I'm having a problem regarding a google chart, with one string it works, if i want to put two strings it doesn't. My code</p>
  
  <pre><code>$results=$stmt-&gt;fetchAll(PDO::FETCH_ASSOC);
      $table = array();
      $table['cols'] = array(
          array('label' =&gt; 'Escola', 'type' =&gt; 'string'),
          array('label' =&gt; 'Dominios', 'type' =&gt; 'string'),
          array('label' =&gt; 'Total', 'type' =&gt; 'number')
      );
      $rows = array();
      foreach($results as $r){
          $temp = array();
          $temp[] = array('v' =&gt; $r['escola']);
          $temp[] = array('v' =&gt; $r['dominio']);
          $temp[] = array('v' =&gt; (int) $r['total']);
          $rows[] = array('c' =&gt; $temp);
      }
      $table['rows'] = $rows;
      $jsonTable = json_encode($table);
      echo $jsonTable;
  </code></pre>
  
  <p>and my chart</p>
  
  <pre><code>&lt;script type="text/javascript"&gt;
  google.load("visualization", "1", {packages:["corechart"], 'language': 'pt'});
  google.setOnLoadCallback(drawVisualization);
  function drawVisualization() {
      var jsonData = null;
      var json = $.ajax({
          url: "xxxxxx.php", // make this url point to the data file
          dataType: "json",
          async: false,
          success: (
              function(data) {
                  console.log(JSON.stringify(data));
                  jsonData = JSON.stringify(data);
                  var data = new google.visualization.DataTable(jsonData);
                  var options = {
                      'legend':'center',
                      'title':'Domínios',
                      'width':800,
                      'height':600,
                      colors: ['#e2431e']
                  }
                  var chart= new google.visualization.ColumnChart(document.getElementById('chart_div')).
                  draw(data, options);
              })
      }).responseText;
  }
  google.setOnLoadCallback(drawVisualization);
  </code></pre>
  
  <p>
  I'm receiving that error each time  the chart is drawed but i don't see where the error is</p>
  
  <p>any help?</p>