title: Why can't I aggregate data.frame with FUN = shapiro.test
body: <p>Here's the data.frame in question :</p>
  
  <pre><code>sample &lt;- dput(df)
  structure(c(6, 5, 5, 4, 4, 7, 5, 4, 6, 6, 5, 6, 8, 6, 3, 5, 8, 
  4, 7, 6, 4, 4, 2, 5, 4, 7, 2, 5, 5, 4, 6, 4, 5, 8, 6, 4, 7, 7, 
  4, 4, 5, 8, 4, 6, 9, 3, 7, 6, 8, 6, 6, 3, 3, 6, 7, 7, 6, 6, 7, 
  7, 6, 7, 8, 3, 5, 5, 4, 6, 4, 7, 3, 4, 6, 3, 5, 5, 7, 6, 7, 4, 
  3, 5, 4, 5, 3, 6, 8, 6, 4, 9, 8, 5, 4, 7, 4, 6, 7, 5, 6, 9, 7, 
  6, 8, 5, 0, 5, 6, 5, 7, 5, 5, 7, 2, 5, 7, 4, 3, 7, 7, 6, 7, 8, 
  5, 6, 9, 4, 6, 7, 5, 4, 5, 4, 6, 6, 9, 8, 5, 7, 7, 7, 4, 7, 6, 
  7, 6, 9, 5, 4, 8, 4, 6, 4, 6, 0, 4, 7, 6, 4, 6, 3, 0, 3, 4, 5, 
  8, 5, 6, 6, 5, 5, 7, 7, 5, 7, 8, 3, 4, 4, 5, 7, 5, 8, 6, 9, 7, 
  5, 4, 3, 4, 4, 6, 2, 4, 6, 7, 6, 5, 5, 5, 5, 6, 6, 8, 5, 5, 6, 
  6, 4, 5, 8, 4, 7, 5, 6, 3, 6, 5, 3, 6, 3, 6, 6, 7, 4, 2, 6, 5, 
  4, 5, 6, 6, 6, 7, 6, 6, 6, 5, 6, 5, 6, 6, 7, 7, 6, 6, 5, 5, 5, 
  7, 6, 9, 8, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
  1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 
  1, 1, 1, 1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 
  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 
  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 
  2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 
  2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 
  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 
  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 
  3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 
  3, 3, 3, 3), .Dim = c(252L, 2L), .Dimnames = list(NULL, c("pMRMW", 
  "group")))
  
  aggregate(pMRMW~group,data=sample,shapiro.test)
  </code></pre>
  
  <p>returns </p>
  
  <pre><code>corrupt data frame: columns will be truncated or padded with NAs
  </code></pre>
  
  <p>Other functions works as expected.</p>
  
  <p>Am I missing something totally obvious ?</p>