title: Documents in training data belongs to a particular topic in LDA
body: <p>I am working on a problem where I have the Text data with around 10,000 documents. I have create a app where if user enters some random comment , It should display all the similar comments/documents present in the training data.
  Exactly like in Stack overflow, if you ask an question it shows all related questions asked earlier.
  So if anyone has any suggestions how to do it please answer.</p>
  
  <p>Second I am trying LDA(Latent Dirichlet Allocation) algorithm, where I can get the topic with which my new document belongs to, but how will I get the similar documents from training data. Also how shall I choose the num_topics in LDA.</p>
  
  <p>If anyone has any suggestions of algorithms other than LDA , please tell me. </p>