title: gnumeric: sum of positive values in a range sans creating new column
body: <p>Using gnumeric, how do I sum the positive values in a range, without 
  creating a new column? </p>
  
  <p>I'm thinking something along the lines of: </p>
  
  <pre><code>SUM(B21:B25, #&gt;0&amp;) 
  </code></pre>
  
  <p>or </p>
  
  <pre><code>SUM(SELECT(B21:B25, #&gt;0&amp;)) 
  </code></pre>
  
  <p>"#>0&amp;" is Mathematica-ese for a function returning true if its 
  argument is greater than 0, false otherwise. </p>
  
  <p>More generically: how do I apply an aggregate function to cells in a 
  range that meet a specific condition? </p>