title: How to concatenate factors, without them being converted to integer level?
body: <p>I was surprised to see that R will coerce factors into a number when concatenating vectors. This happens even when the levels are the same. For example:</p>
  
  <pre><code>&gt; facs &lt;- as.factor(c("i", "want", "to", "be", "a", "factor", "not", "an", "integer"))
  &gt; facs
  [1] i       want    to      be      a       factor  not     an      integer
  Levels: a an be factor i integer not to want
  &gt; c(facs[1 : 3], facs[4 : 5])
  [1] 5 9 8 3 1
  </code></pre>
  
  <p>what is the idiomatic way to do this in R (in my case these vectors can be pretty large)? Thank you.</p>