title: n'th largest value of rows in a data frame and related column name
body: <p>Let I have a data frame(df1)</p>
  
  <p>df1:</p>
  
  <pre><code>v1    v2    v3    v4
  --    --    --    --
  4.1   1.2   12    1.4
  14    18.4  15.1  6.9
  </code></pre>
  
  <p>I want to find nth largest value of each row and also column name of that value.</p>
  
  <p>Foe example, let say I want to find second largest value of each row and related column name. So the output(df2) sould be:</p>
  
  <p>df2:</p>
  
  <pre><code>value   col_name
  ---     --------
  4.1     v1
  15.1    v3
  </code></pre>
  
  <p>How can I do that using R? I will be very glad for any help. Thanks a lot.</p>