title: dplyr::recode Why does pipe generate error?
body: <p>If I use recode in a pipe, I get an error:</p>
  
  <pre><code>df &lt;-  df %&gt;%
    recode(unit, .missing="g")
  </code></pre>
  
  <blockquote>
    <p>Error in UseMethod("recode") : no applicable method for 'recode'
    applied to an object of class "c('tbl_df', 'tbl', 'data.frame')"</p>
  </blockquote>
  
  <p>If I pull it out of the pipe, it works fine:</p>
  
  <pre><code>df$unit &lt;- recode(df$unit, .missing="g")
  </code></pre>
  
  <p>Any ideas why?  I'd like to stay in the pipe if possible.</p>