title: Conditional Sum (variable)
body: <p>A report in iReport (4.0.1) with various fields includes: <code>$F{value}</code> (Integer) and <code>$F{created_at}</code>.</p>
  
  <p>I'd like to calculate variables that would give:</p>
  
  <ol>
  <li>the sum of <code>$F{value}</code> when <code>$F{created_at}</code> is before a given date</li>
  <li>the sum of <code>$F{value}</code> when <code>$F{created_at}</code> is after a given date</li>
  </ol>
  
  <p>Any idea how this could be done?</p>