title: R Error using readHTMLTable
body: <p>I am using the following code:</p>
  
  <pre><code>url  = "http://finance.yahoo.com/q/op?s=DIA&amp;m=2013-07"
  
  library(XML)
  tabs = readHTMLTable(url, stringsAsFactors = F)
  </code></pre>
  
  <p>I get the following error:</p>
  
  <pre><code>Error: failed to load external entity "http://finance.yahoo.com/q/op?s=DIA&amp;m=2013-07"
  </code></pre>
  
  <p>When I use the url in the browser it works fine. So, what am I doing incorrect here?</p>
  
  <p>Thanks</p>