title: Count rows and sum r
body: <p>I want to sum data by date but I don't know how to do this.</p>
  
  <p>My data looks like</p>
  
  <pre><code>    date      LIKE  LOVE  WOW HAHA SAD  ANGRY
  1 2016-02-25   949    0   3    0   0     2
  2 2016-02-25 12653   14   0    0   1     0
  3 2016-02-24  2981    0   7    3   10     0
  4 2016-02-24  2500    6   0    3   0     5
  </code></pre>
  
  <p>My proposal is </p>
  
  <pre><code>    date      LIKE  LOVE  WOW HAHA SAD  ANGRY
  1 2016-02-25 13602   14   3    0   1     2
  2 2016-02-24  5481    6   7    6   10    5
  </code></pre>
  
  <p>How can I achieve this?</p>