title: How to check if a column exists in a matrix or data frame?
body: <p>Is there a way to check if a column exist in a matrix or data.frame?</p>
  
  <p>For example: TableA</p>
  
  <pre><code>Name    Age    Address     Contact No.
  Ben     12     CA           1234567
  </code></pre>
  
  <p>How can I check if a column "Gender" or "Age" exist before I process a row?</p>
  
  <p>Thanks</p>