title: Column stacked chart by groups
body: <p>I have a column chart that shows power consumption in current and previous years. Now this consumption comes from different sources, so I would like to chart these values in multiple columns that show stacked values.</p>
  
  <p>I am using google chart, but setting the <code>isStacked</code> parameter to <code>true</code> in the options array just stacks every single value for a specific row. What I want to do achieve is something like this:</p>
  
  <p><img src="https://i.stack.imgur.com/Xreew.gif" alt="enter image description here"></p>
  
  <p>That is, rows with multiple stacked columns. Is this even possible with Google Chart API?</p>