title: R markdown df_print options
body: <p>I have a R markdown document in RStudio, where a data.table is printed.  I want to set the data frame print options to control printed number of rows and columns, as described <a href="http://rmarkdown.rstudio.com/html_document_format.html#data_frame_printing" rel="noreferrer">here</a>.</p>
  
  <p>Here is a minimal example .Rmd file:</p>
  
  <pre><code>---
  output: 
    html_document: 
      fig_height: 8
      fig_width: 10
      df_print: paged
  ---
  
  ```{r}
  knitr::opts_chunk$set(echo = FALSE)
  cars
  ```
  </code></pre>
  
  <p><strong>Where/how do I set the <code>rows.print</code> option?</strong></p>
  
  <p>I've tried this:</p>
  
  <pre><code>---
  output: 
    html_document: 
      fig_height: 8
      fig_width: 10
      df_print: paged
      rows.print: 25
  ---
  </code></pre>
  
  <p>which doesn't work (still at default 10 rows), and this:</p>
  
  <pre><code>```{r}
  knitr::opts_chunk$set(echo = FALSE, rows.print=25)
  cars
  ```
  </code></pre>
  
  <p>which also doesn't work.</p>