How do I include sections of R code within my LaTeX document?

We recommend the listings package for including R code in LaTeX documents. If you add

\usepackage{listings}

to your preamble, you can then insert R code as demonstrated in this example:

\documentclass{article}
\usepackage{listings}
\begin{document}
\begin{lstlisting}[language=R]
fib <- function(n) {
  if (n < 2)
    n
  else
    fib(n - 1) + fib(n - 2)
}
fib(10) # => 55
\end{lstlisting}
\end{document}

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This example produces the following output:

Our article on using Knitr may also be of interest.