title: R: Error Message of cast "unimplemented type 'list' in 'listgreater"
body: <p>Using the following commands (x is a table with 3 columns A, B and C)</p>
  
  <pre><code>library(reshape)
  cast(x, A~B)
  </code></pre>
  
  <p>Following error appears:</p>
  
  <pre><code>Using C as value column.  Use the value argument to cast to override this choice
  Error in order(A = list("xxx",  : 
    unimplemented type 'list' in 'listgreater'
  </code></pre>
  
  <p>What does it means and how to solve it?</p>
  
  <hr>
  
  <p>I guess it maybe due to the dataframe's data format (correct me if I am wrong).  As i did a test of the format of the table x and y with str command.</p>
  
  <pre><code>str(x) returns
  $ A: List of 6
  ..$ : chr "xxx"
  ....
  $ B:chr "yyy" "yy2" ....
  ...
  $ C: List of 6
  ..$ : num 22.....
  ...
  </code></pre>
  
  <p>For another table y with column D E and F,  no error message appears when I run the cast command.</p>
  
  <pre><code>str(y) shows that all D E F columns are Factor w/ 6 levels....
  </code></pre>
  
  <p>How can I make cast work for list and num containing dataframe x?</p>