title: Quanteda R: How to remove numbers or symbols "from"/"in" a token?
body: <p>I have a question regarding the language pre-processing in quanteda R. I want to generate a document-feature matrix based on some documents. So, I generated a corpus and run the following code.</p>
  
  <pre><code>data &lt;- read.csv2("abstract.csv", stringsAsFactors = FALSE)
  corpus&lt;-corpus(data, docid_field = "docname", text_field = "documents")
  dfm &lt;- dfm(corpus, stem = TRUE, remove = stopwords('english'),
             remove_punct = TRUE, remove_numbers = TRUE, 
             remove_symbols = TRUE, remove_hyphens = TRUE)
  </code></pre>
  
  <p>When I examined the dfm I noticed some tokens (<code>#ml, @attribut, _iq, 0.01ms</code>). I rather want to have (<code>ml, attribut, iq, ms</code>).</p>
  
  <p>I thought I deleted all the symbols and numbers. Why do I still get them?</p>
  
  <p>I'd be glad to get some help.</p>
  
  <p>Thanks!!!</p>