title: How to add group band on combination of multiple fields?
body: <p>I have this data and I want in iReport is group this by number group and color group.</p>
  
  <pre><code>color | number_group | color_group |
  red   |    1         |  primary    |
  blue  |    1         |  primary    |
  yellow|    2         |  primary    |
  orange|    2         |  secondary  |
  violet|    1         |  secondary  |
  green |    1         |  secondary  |
  </code></pre>
  
  <p>I want in my report</p>
  
  <pre><code>Color Group: Primary   Number: 1
  red
  blue
  
  Color Group: Primary   Number: 2
  yellow
  
  Color Group: Secondary Number: 1
  violet
  green
  
  Color Group: Secondary Number: 2
  orange
  </code></pre>
  
  <p>But in I can only manage to do <strong><em>Add Group > Group Criteria > Group by following expression > choose color_group</em></strong> field.</p>
  
  <p>And the output is this which is not the one that I'm hoping for.</p>
  
  <pre><code>Color Group: Primary Number: 1
  red
  blue
  yellow
  
  Color Group: Secondary Number: 2
  orange
  violet
  green
  </code></pre>
  
  <p>I think the right solution is using <strong><em>Add Group > Group Criteria > Group by following expression > group expression with text area</em></strong> but I don't know what to put there. Anyone?</p>