title: How to use greek letters in fig.caption using RMarkdown?
body: <p>This code produces an error when I try to knit a pdf using <em>RMarkdown</em> in <em>RStudio</em>.</p>
  
  <p>How can I write a greek letter in <em>fig.caption</em> as for example $\beta$?</p>
  
  <pre><code>---
  title: "Untitled"
  author: "SB"
  date: "Thursday, January 29, 2015"
  output: 
    pdf_document:
    fig_caption: yes
  ---
  
  
  ```{r var, echo=FALSE, fig.cap="Cars variation rate between year $t$ and $t-1$ for $0 &lt; \beta &lt; 1$"}
  plot(cars)
  ```
  </code></pre>