title: DocumentTermMatrix needs to have a term frequency weighting Error
body: <p>I'm trying to use LDA() from topicmodels package on a quite large data set. After trying everything to fix the following errors "In nr * nc : NAs produced by integer overflow" and  "Each row of the input matrix needs to contain at least one non-zero entry", I ended up with this error. </p>
  
  <pre><code>ask&lt;- read.csv('askreddit201508.csv', stringsAsFactors = F)    
  myDtm &lt;- create_matrix(as.vector(ask$title), language="english", removeNumbers=TRUE, stemWords=TRUE, weighting=weightTf)
  myDtm2 = removeSparseTerms(myDtm,0.99999)
  myDtm2 &lt;- rollup(myDtm2, 2, na.rm=TRUE, FUN = sum)
  rowTotals &lt;- apply(myDtm2 , 1, sum)
  myDtm2   &lt;- myDtm2[rowTotals&gt; 0, ]  
  LDA2 &lt;- LDA(myDtm2,100)
  
  Error in LDA(myDtm2, 100) : 
    The DocumentTermMatrix needs to have a term frequency weighting
  </code></pre>