title: BIRT Mathematics on data set
body: <p>I am pretty new to Birt reporting, i can make simple charts and tables, bet when it comes to some calculation of values from data sets - i have no clue in which direction should i watch. </p>
  
  <p>For example i have this simple data set:</p>
  
  <pre>
  count1   count2   max   type   lenght
  616      3858     21    STEEL    20
  723      4432     14    STEEL    40
  854      5869     21     ALL     20
  838      5225     14     ALL     40
  </pre>
  
  <p>And i would like to have Birt to calculate approximately this:</p>
  
  <pre>SUM(count2)/SUM(count1) WHERE  type=ALL</pre>
  
  <p>so this</p>
  
  <pre>((5869+5225)/(854+838))</pre>
  
  <p>My question would be how could i get there. At this point i think i would need just the right direction how these kind of operations could be made.</p>
  
  <p>Thanks in advance.</p>