title: Remove both float64 values if found in either columns Pandas
body: <p>I'm trying to remove all rows if a non unique value is found example below:</p>
  
  <pre><code>    N1  N2
  1   2   4
  2   4   5
  3   6   6
  4   8   7
  5   10  8
  6   12  10
  7   NaN 12
  8   NaN 14
  </code></pre>
  
  <p>So in this instance the values I want is 2 5 7 and 14. Also one column is longer than the other and hence has to ignore NaN. I basically want to find repeating values and delete both from N1 and N2. This is what I tried:</p>
  
  <p><code>df[~df.N1.isin(['N2'])]</code></p>
  
  <p>Got some error. Thank you for your help.</p>
  
  <p>Kevin</p>