How to label a code section in Sweave

Question

I'm new to sweave and was wondering what is the appropriate way to label a code section. For example, if I have:

<<echo= true>>=
x<-5
y<-x+5
@

How would I get it to put a either above it or below it, with something like "Code Example 1". I would like something similar to how you can label figures or tables in LaTeX.

Answer 1

In LaTeX captions can be used within float environments like figures or tables. So if your R output is e.g. a figure you can enclose it in a figure environment:

\begin{figure}

<<fig=TRUE, echo=FALSE, eps=TRUE>>=
  data(iris)
  boxplot(iris[,2]~iris[,5])
@

\caption{A boxplot of the famous Fisher data set.}
\end{figure}

If you want your R-Code as a float environment (with the possibility to use \caption) you will have to define your own float environment. Have a look at LaTeX WikiBook. Something like the following will do it:

In your document preamble:

\usepackage{float}
\newfloat{rcode}{h!t}{rcode}
\floatname{rcode}{Code Example}

Then in your document body:

\begin{rcode}
<<echo=true>>=
x<-5
y<-x+5
@
\caption{This code shows something.}
\end{rcode}

Answer 2

Try something like this:

<<label = MyChunk, echo= true>>=
x<-5
y<-x+5
@