title: stemCompletion is not working
body: <p>I am using tm package for text analysis of repair data, Reading data into data frame, converting to Corpus object, applied various methods to clean data using lower, stipWhitespace, removestopwords and so on.</p>
  
  <p>Taken back of Corpus object for stemCompletion.</p>
  
  <p>Performed stemDocument using tm_map function, my object words got stemmed </p>
  
  <p>got results at expected.</p>
  
  <p>When I am running stemCompletion operation using tm_map function, it is not working
  and got below error</p>
  
  <blockquote>
    <p>Error in UseMethod("words") :    no applicable method for 'words'
    applied to an object of class "character"</p>
  </blockquote>
  
  <p>Executed trackback() to show and got steps as below</p>
  
  <pre><code>&gt; traceback()
  9: FUN(X[[1L]], ...)
  8: lapply(dictionary, words)
  7: unlist(lapply(dictionary, words))
  6: unique(unlist(lapply(dictionary, words)))
  5: FUN(X[[1L]], ...)
  4: lapply(X, FUN, ...)
  3: mclapply(content(x), FUN, ...)
  2: tm_map.VCorpus(c, stemCompletion, dictionary = c_orig)
  1: tm_map(c, stemCompletion, dictionary = c_orig)
  </code></pre>
  
  <p>How can I resolve this error?</p>