title: Change column variable string from "1" to "01"
body: <p>I have a column in a dataframe that is a charachter type. The variables are a mix of 1, 01, 2, 01, 3, 03, 4, 04 etc.</p>
  
  <p>How would I select all without a leading '0' and format so they are all 01, 02, 03, 04 etc</p>