title: R - Verifying That A Column Only Has Certain Values
body: <p>I am trying to figure out how to verify that that columns of a spreadsheet only contain a predetermined set of values.  Any thoughts on the best way to do this?</p>
  
  <p>To provide an example, I am using the following method to determine that the number of columns is correct.</p>
  
  <pre><code>if(!ncol(data_read) == 9){
      print("There are not 9 columns in this file")
      return(FALSE)
  } else if{
    OTHER PARAMETERS HERE (such as the one I'm trying to figure out)
    }
  
     return(TRUE}
   }
  </code></pre>