title: change data frame so thousands are separated by dots
body: <p>At the moment, I'm working with RMarkdown and Pandoc. My data.frames in R look like this:</p>
  
  <pre><code>3.538e+01 3.542e+01 3.540e+01
  9.583e+00 9.406e+00 9.494e+00
  2.601e+05 2.712e+05 5.313e+05
  </code></pre>
  
  <p>After I ran pandoc, the result looks like this:</p>
  
  <pre><code>35.380 35.420 35.400
  9.583 9.406 9.494
  260116.000 271217.000 531333.000
  </code></pre>
  
  <p>What it should look like is:</p>
  
  <pre><code>35,380 35,420 35,400
  9,583  9,406  9,494
  260.116 271.217 531.333
  </code></pre>
  
  <p>So I want commas instead of dots and I want no comma or dot after 260116 (thousand numbers). The dots to separate the thousand would be nice. Is there a way to directly Change the appearance in R or do I have to set options in knitr/markdown?   </p>
  
  <p>Thanks</p>