title: sum function in GREL in OpenRefine
body: <p>In OpenRefine, I'm trying to increase the value of every number in a column by 1.</p>
  
  <p>The GREL expression <code>sum([value],1)</code> gives me <code>Error: sum expects an array of numbers</code>. </p>
  
  <p>I guess I don't know how to produce an array of numbers. When I use a different function on the same column, such as <code>tan([value])</code>, I get the result I want.</p>