title: kdb how to pass a column name into a function
body: <p>As a simplifying example, I have </p>
  
  <pre><code>tbl:flip `sym`v1`v2!(`a`b`c`d; 50 280 1200 1800; 40 190 1300 1900)
  </code></pre>
  
  <p>and I d like to pass a column name into a function like</p>
  
  <pre><code>f:{[t;c];:update v3:2 * c from t;} 
  </code></pre>
  
  <p>In this form it doesnt work. any suggestion how I can make this happen?
  Thanks</p>