title: Necessary to apply TF-IDF to new documents in gensim LDA model?
body: <p>I'm following the 'English Wikipedia' gensim tutorial at <a href="https://radimrehurek.com/gensim/wiki.html#latent-dirichlet-allocation" rel="noreferrer">https://radimrehurek.com/gensim/wiki.html#latent-dirichlet-allocation</a></p>
  
  <p>where it explains that tf-idf is used during training (at least for LSA, not so clear with LDA).</p>
  
  <p>I expected to apply a tf-idf transformer to new documents, but instead, at the end of the tut, it suggests to simply input a bag-of-words.</p>
  
  <pre><code>doc_lda = lda[doc_bow]
  </code></pre>
  
  <p>Does LDA require bag-of-words vectors only?</p>