title: Emulate split() with dplyr group_by: return a list of data frames
body: <p>I have a large dataset that chokes <code>split()</code> in R. I am able to use <code>dplyr</code> group_by (which is a preferred way anyway) but I am unable to persist the resulting <code>grouped_df</code> as a list of data frames, a format required by my consecutive processing steps (I need to coerce to <code>SpatialDataFrames</code> and similar).</p>
  
  <p>consider a sample dataset:</p>
  
  <pre><code>df = as.data.frame(cbind(c("a","a","b","b","c"),c(1,2,3,4,5), c(2,3,4,2,2)))
  listDf = split(df,df$V1)
  </code></pre>
  
  <p>returns </p>
  
  <pre><code>$a
     V1 V2 V3
   1  a  1  2
   2  a  2  3
  
  $b
     V1 V2 V3
   3  b  3  4
   4  b  4  2
  
  $c
     V1 V2 V3
   5  c  5  2
  </code></pre>
  
  <p>I would like to emulate this with <code>group_by</code> (something like <code>group_by(df,V1)</code>) but this returns one, <code>grouped_df</code>. I know that <code>do</code> should be able to help me, but I am unsure about usage (also see <a href="https://stackoverflow.com/questions/26796829/how-can-dplyr-generate-data-frame-for-each-group-after-the-group-by-opration/26798420?noredirect=1#comment55284955_26798420">link</a> for a discussion.)</p>
  
  <p>Note that split names each list by the name of the factor that has been used to establish this group - this is a desired function (ultimately, bonus kudos for a way to extract these names from the list of dfs).</p>