title: Tooltip in Google Chart while populating chart using JSON
body: <p>I am populating my Google chart using JSON currently, but I need to customize tooltips as well. Currently my JSON looks like this: </p>
  
  <pre><code>{
      "cols": [
          {"id": "", "label": "date", "type": "string"},
          {"id": "", "label": "price", "type": "number"}
      ],
      "rows": [
          {"c":[{"v": "Apr 24th","f":null}, {"v": 56000,"f":"56000"}]},
          {"c":[{"v": "May 3rd","f":null}, {"v": 68000,"f":"68000"}]},
          {"c":[{"v": "May 13th","f":null}, {"v": 50400,"f":"50400"}]}
      ]
  }
  </code></pre>
  
  <p>But if I specify my tooltip in the JSON too like this:</p>
  
  <pre><code>{
      "cols": [
          {"id": "", "label": "Date", "type": "string"},
          {"id": "", "label": "price", "type": "number"},
          {"id": "", "role": "tooltip", "type": "string"}
      ],
      "rows": [
          {"c":[{"v": "Apr 24th","f":"null"}, {"v": 56000,"f":"56000"}, {"v": "24 April, Price - 56000, Seller-abcd"}]},
          {"c":[{"v": "May 3rd","f":"null"}, {"v": 68000,"f":"68000"}, {"v": "3 May, Price - 68000, Seller-abcd"}]},
          {"c":[{"v": "May 13th","f":"null"}, {"v": 50400,"f":"50400"}, {"v": "23 May, Price - 50000, Seller-abcd"}]}
      ]
  }
  </code></pre>
  
  <p>I get an error that all values in series should be of same data type. </p>
  
  <p>My client side code looks like this: </p>
  
  <pre><code>var jsonData = $.ajax({
      url: '../phps/testPhp.php',
      dataType:"json",
      async: false
  }).responseText;
  
  var dataTable = new google.visualization.DataTable(jsonData);
  
  var minVal = 50000;
  var maxVal = 70000;    
  
  var chart = new google.visualization.LineChart(document.getElementById('chart_div'));
  
  var options = {
      width: 375, height: 240,
      legend: 'none',
      pointSize: 5,
      backgroundColor: 'transparent',
      vAxis: { minValue: 45000, maxValue: 70000 }
  };
  
  chart.draw(dataTable, options);
  </code></pre>
  
  <p>Please let me know if someone knows the solution.</p>