title: Google visualization API - Stacked Bar Chart - Custom Tooltip
body: <p>I've been trying to get a custom tooltip for a stacked bar chart.</p>
  
  <pre><code>var data = new google.visualization.DataTable();
  data.addColumn('string', 'Units');
  data.addColumn('number', '1');
  data.addColumn('number', '2');
  data.addColumn('number', '3');
  data.addColumn('number', '4');
  
  _1 = 0.123
  _2 = 0.23
  _3 = 0.3
  _4 = 0
  
  data.addRow([_units, _1, _2, _3, _4,]);
  
  var options = {
          isStacked: true,
          height: 150,
          chartArea: { height: 50 },
          legend: { position: 'top' },
  };
  
  bchart = new google.visualization.BarChart(bcontainer);
  bchart.draw(data, options);
  </code></pre>
  
  <p>My question then is how to create a tooltip for each: _1, _2, _3, _4?</p>
  
  <p>Thanks</p>