title: Aggregating from multiple columns in Tableau
body: <p>I have a table that looks like:</p>
  
  <pre><code>id     aff1    aff2    aff3    value
  1       a        x      b        5
  2       b        c      x        4
  3       a        b      g        1
  </code></pre>
  
  <p>I would like to aggregate the aff columns to calculate the sum  of "value" for each aff. For example, the above gives:</p>
  
  <pre><code>aff    sum
  a       6
  b       10
  c       4
  g       1
  x       9
  </code></pre>
  
  <p>Ideally, I'd like to do this directly in tableau without remaking the table by unfolding it along all the aff columns.</p>