title: Differing frequency count between grpel and quanteda textstat_frequency
body: <p>I was validating some data and I noticed that when I use grepl to search for a term using <code>sum(grepl('time',x = df$Comments))</code> (where df is a simple data.frame where each row contains a different tweet) and I try to compare that to <code>textstat_frequency</code> in the quanteda package using</p>
  <pre><code>df %&gt;% corpus(text_field='Comments') %&gt;% dfm(tolower = T,
                                               remove = stop_words,
                                               remove_punct = T,
                                               remove_symbols = T,
                                               remove_numbers = T) %&gt;% textstat_frequency()
  </code></pre>
  <p>I get two different results</p>
  <p>with grepl, i'm getting 2718 and with quanteda I'm getting:</p>
  <pre><code> feature frequency rank docfreq group
    time      2879    1    2113   all
  </code></pre>
  <p>Is textstat_frequency not the way to go about this?</p>