title: How to split a data frame in the order I want?
body: <p>I have a data frame df like this</p>
  
  <pre>
  df 
  x     y   id
  10   5     2
  12   10    2
  15   0     1
  </pre>
  
  <p>I want to split by the id. I used <code>split(df, df$id)</code> and I get</p>
  
  <pre>
  x   y   id
  15  0   1
  </pre>
  
  <p>and</p>
  
  <pre>
  x   y    id
  10  5    2
  12  10   2
  </pre>
  
  <p>But I want the one with id=2 to come before than the one with id =1
  So basically I want the output to be</p>
  
  <pre>
  x     y     id
  10   5      2
  12   10     2
  </pre>
  
  <p>and</p>
  
  <pre>
  x    y    id
  15   0    1
  </pre>