title: Group by two column and summarize multiple columns
body: <p>I have a data frame and I would like to group by the column &quot;State&quot; and  &quot;Date&quot; and then summarize the values of the other columns something like this.</p>
  <p>df</p>
  <pre><code>State  Female  Male   Date
  ------------------------------
  Texas  2       2     01/01/04
  Texas  3        1     01/01/04
  Texas  5        4     02/01/04
  Cali   1        1     05/06/05
  Cali   2        1     05/06/05
  Cali   3         1    10/06/05
  Cali   1         2     10/06/05
  NY    10         5    11/06/05
  NY    11         6    12/06/05
  
  </code></pre>
  <p>Outcome expected</p>
  <p>df</p>
  <pre><code>State  Female  Male   Date
  ------------------------------
  Texas  5       3     01/01/04
  Texas  5        4     02/01/04
  Cali   3        2     05/06/05
  Cali   4         3    10/06/05
  NY    10         5    11/06/05
  NY    11         6    12/06/05
  
  </code></pre>
  <p>I tried with group by and summarize but I don´t exactly how con I do the same for 2 columns</p>
  <p>My try</p>
  <pre><code>df &lt;- df_homicides %&gt;% 
          group_by(state) %&gt;% 
          summarise(Female = sum(Female))
  
  ``
  Thanks for your help!
  </code></pre>