title: Generating knitr reports
body: <p>I'm pretty new to <code>knitr</code>, but I've written a script that generates a report for a county. One of the first lines in the first code chunk is <code>display_county &lt;- "King"</code>, and it queries a database to make all sorts of nice things about King County. Now I want to create reports for every county in my state. The only line in the script that needs be changed is the definition of <code>display_county</code>.</p>
  
  <p>I know the <code>brew</code> packages is set up for stuff like this, and I know there's overlap between <code>brew</code> and <code>knitr</code>, but I don't know what I should be using. </p>
  
  <p><a href="https://stackoverflow.com/a/8437769/903061">This answer using Brew and Sweave</a> would work with minor modifications, but is there a nice <code>knitr</code> way to bypass <code>brew</code>?</p>