title: Google Chart: Get Column Count in Dashboard for Bar Chart
body: <p>I have a JSON data like below to build a dashboard in google chart.
  I would like to draw a monthly bar chart with x-axis as scan_time (Month) and y-axis as count of tag_id's that comes into that month. The tag_ids can be duplicate.</p>
  
  <p>Input data in JSON:</p>
  
  <pre><code> [ 
         {  
            "tag_id":"04:0f",
            "scan_time":"2016-09-29 06:47:47",
         },
         {  
            "tag_id":"04:0f",
            "scan_time":"2016-09-29 14:48:42",
         },
         {  
            "tag_id":"99:9n",
            "scan_time":"2016-10-29 06:47:47",
         },
         {  
            "tag_id":"05:m8",
            "scan_time":"2016-11-29 06:48:42",
         }
      ]
  </code></pre>
  
  <p>something like </p>
  
  <pre><code>Month       Count
      Sept        2
      Oct         1
      Nov         1
  </code></pre>