title: Variance failure in R markdown
body: <p>I have a dataset in R, and at one point take the variance of six values (0.156, 0.128, 0.159, 0.171, 0.140, 0.157).  Running this code in the R console is fine--R spits out 0.0002341667.  However, when I run the same operation in Knitr to produce a PDF, I get the following error: </p>
  
  <pre><code>! Missing $ inserted.
  &lt;inserted text&gt; 
                  $
  l.395 2.3416667\times
  pandoc.exe: Error producing PDF from TeX source
  Error: pandoc document conversion failed with error 43
  </code></pre>
  
  <p>If I take the square root, the error doesn't happen.  Any thoughts?  My code (excluding pulling from my source) is below.</p>
  
  <pre><code>values &lt;- c(0.156, 0.128, 0.159, 0.171, 0.140, 0.157)
  var(values)
  </code></pre>