28.27 Referencing Chunks in LaTeX
REVIEW We may like to reference code chunks
from other parts of our document. LaTeX handles cross references
nicely, and there are packages that extend this to user defined cross
references. The amsthm package provides one such mechanism.
To add a cross referencing capability we can tell LaTeX to use the
amsthm package and to create a new theorem environment called
rcode by including the following in the document preamble
(prior to the \begin{document}):
\usepackage{amsthm}
\newtheorem{rcode}{R Code}[section]We then tell knitr (Xie 2024) to add an rcode environment
around the chunks. The following chunk achieves this by adding some
code to a hook function for knitr (Xie 2024). This will typically
also be in the preamble of the document, though not necessarily.
<<setup, include=FALSE}
knit_hooks$set(rcode=function(before, options, envir)
{
if (before)
sprintf('\\begin{rcode}\ {#%s}l{}', options$label)
else
'\\end{rcode}'
})
@Once we’ve done that, we add rcode=TRUE for those chunks we
wish to refer to. Here is a chunk as an example:
<<demo_chunk_ref, rcode=TRUE}
seq(0, 10, 2)
@ The output from the chunk is:
## [1] 0 2 4 6 8 10We can then refer to the R code chunk with
\@ref(demo_chunk_ref), which prints the R Code reference number
as @ref(demo_chunk_ref), and \pageref{demo_chunk_ref}, which
prints the page number as .
References
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