R and presentations: a basic example of knitr and beamer

Manually combining R code and a presentation can be quite a pain. Luckily, using tools like odfWeave, Sweave and knitr, integrating documents and R code is quite painless. In this post I want to take a look at combining the knitr package with the Latex package beamer. I use the knitr package instead of the the Sweave package because it basically is a better Sweave, see this link for more information.

The basic structure of a knitr document is that you fill your text file with latex code, interspaced with section of R code like this:

<<name_of_chunk>>=
some R code here
@

It is custom to save this file with a .Rnw extension. Going from the Rnw to a pdf is a two step procedure: 1) run knitr, and 2) run pdflatex. First, knitr interprets the R code to produce a tex file, and then pdflatex creates the pdf. Below I posted a basic example which shows how to use knitr together with the beamer document class. The resulting pdf looks like this, and this is the knitr/latex code (Rnw file) that was the source.

\documentclass{beamer}

\begin{document}

\title{A Minimal Demo of knitr}
\author{Yihui Xie}

\maketitle

\begin{frame}[fragile]
You can test if \textbf{knitr} works with this minimal demo. OK, let's
get started with some boring random numbers:

<<boring-random>>=
set.seed(1121)
(x=rnorm(20))
mean(x);var(x)
@
\end{frame}

\begin{frame}[fragile]
The first element of \texttt{x} is \Sexpr{x[1]}. Boring boxplots
and histograms recorded by the PDF device:

<<boring-plots,dev=pdf,fig.width=5,fig.height=5,out.width=.45\linewidth,par=TRUE>>=
## two plots side by side (option fig.show=hold)
boxplot(x)
hist(x,main='')
@
\end{frame}

\end{document}