title: jasper reports, group data in bar chart
body: <p>I need to create a report with total of activities in months. I am using  <code>JRBeanCollectionDataSource</code> to fill data in report like </p>
  
  <p><img src="https://i.stack.imgur.com/JalPE.png" alt="example1"></p>
  
  <p>Also I need to add a <strong>Bar Chart</strong> like </p>
  
  <p><img src="https://i.stack.imgur.com/ZXoAv.png" alt="example2"></p>
  
  <p>In my jasper file, I have </p>
  
  <pre><code>&lt;categoryDataset&gt;
      &lt;dataset incrementType="Column"/&gt;
      &lt;categorySeries&gt;
          &lt;seriesExpression&gt;&lt;![CDATA["Complete"]]&gt;&lt;/seriesExpression&gt;
          &lt;categoryExpression&gt;&lt;![CDATA["Complete"]]&gt;&lt;/categoryExpression&gt;
          &lt;valueExpression&gt;&lt;![CDATA[$F{complete}]]&gt;&lt;/valueExpression&gt;
          &lt;labelExpression&gt;&lt;![CDATA["Complete"]]&gt;&lt;/labelExpression&gt;
      &lt;/categorySeries&gt;
      &lt;categorySeries&gt;
          &lt;seriesExpression&gt;&lt;![CDATA["To do"]]&gt;&lt;/seriesExpression&gt;
          &lt;categoryExpression&gt;&lt;![CDATA["To do"]]&gt;&lt;/categoryExpression&gt;
          &lt;valueExpression&gt;&lt;![CDATA[$F{todo}]]&gt;&lt;/valueExpression&gt;
          &lt;labelExpression&gt;&lt;![CDATA["To do"]]&gt;&lt;/labelExpression&gt;
      &lt;/categorySeries&gt;
      &lt;categorySeries&gt;
          &lt;seriesExpression&gt;&lt;![CDATA["Errors"]]&gt;&lt;/seriesExpression&gt;
          &lt;categoryExpression&gt;&lt;![CDATA["Errors"]]&gt;&lt;/categoryExpression&gt;
          &lt;valueExpression&gt;&lt;![CDATA[$F{errors}]]&gt;&lt;/valueExpression&gt;
          &lt;labelExpression&gt;&lt;![CDATA["Errors"]]&gt;&lt;/labelExpression&gt;
      &lt;/categorySeries&gt;
  &lt;/categoryDataset&gt;
  </code></pre>
  
  <p>But I get this error:</p>
  
  <p><img src="https://i.stack.imgur.com/O3mQM.png" alt="error pic"></p>
  
  <p><strong>Where I only get the last value of my query</strong></p>
  
  <p>can I group by month data? like in the second picture?</p>