title: duplicate a column in pyspark data frame
body: <p>I have a data frame in <code>pyspark</code> like sample below. I would like to duplicate a column in the data frame and rename to another column name.</p>
  
  <pre><code>Name    Age    Rate
  Aira     23     90
  Ben      32     98
  Cat      27     95
  </code></pre>
  
  <p>Desired output is :</p>
  
  <pre><code>Name    Age     Rate     Rate2
  Aira    23      90       90
  Ben     32      98       98
  Cat     27      95       95
  </code></pre>
  
  <p>How can I do it? </p>