title: Unable to groupby the column and return the department name, with no of employees respectively and salary range
body: <p><strong>Unable to groupby the column and return the department name, with no of employees respectively and salary range.</strong></p>
  <p>Actual DataFrame is :</p>
  <pre><code>    Name      Dept     Salary   RcvDate
  0   Vertie    IT        3000    2018-08-05
  1   Charlsie  IT        2000    2018-08-05
  2   Manual    IT        4000    2018-08-05
  3   Trudi     IT        6000    2018-08-05
  4   Chong     IT        5600    2018-08-05
  7   Deedee    IT        20000   2018-08-06
  8   Ramonita  Admin     9500    2018-08-06
  9   Terica    Admin     8900    2018-08-06
  10  Hyman     Admin     7200    2018-08-06
  11  Alysha    Admin     4400    2018-08-06
  13  Mackenzie Admin     8700    2018-08-06
  14  Amparo    Admin     9100    2018-08-06
  15  Tabitha   Admin     6500    2018-08-06
  16  Burl      Admin     6000    2018-08-06
  17  Pok       Admin     5600    2018-08-06
  18  Junie     Admin     9500    2018-08-06
  19  Rodrick   Admin     8900    2018-08-06
  20  Maryln    Support   7200    2018-08-06
  21  Tina      Support   4400    2018-08-07
  22  Wilson    Support   6500    2018-08-07 
  </code></pre>
  <p>I'm attaching the code below</p>
  <pre><code>dataset.drop_duplicates(subset=['Dept'], keep='first')
  </code></pre>
  <p>The output is :</p>
  <pre><code>    Name      Dept     Salary   RcvDate
  0   Vertie    IT        3000    2018-08-05
  8   Ramonita  Admin     9500    2018-08-06
  20  Maryln    Support   7200    2018-08-06
  </code></pre>