title: How to add leading zeros of varying length in R dataframe
body: <p>I have a dataframe where the row names have different total digits. There are 152 rows. How do I add leading zeroes when different rows need a different number of leads to achieve the max 8 digits? </p>
  
  <pre><code>row.names
  4921103 
  42106   
  19562106    
  11102
  3435467
  </code></pre>