\documentclass[11pt]{article}
\title{My First Sweave Document}
\author{Roger D. Peng}
\begin{document}
\maketitle
\section{Introduction}
This is some text (i.e. a ``text chunk'').   
Here is a code chunk
<<simulation,echo=false>>=
set.seed(1)
x <- rnorm(100)
mean(x)
@
\end{document}