Extracting Code of R function to be used in knitr with controled width

We can use formatR::usage(lm) to get the arguments of lm function and can use the following command to redirect the output to knitr :

<<test, code=formatR::usage(lm), eval=FALSE>>=
@

I wonder if there is such function to get the lm function code to redirect to knitr .

Edited

Got the code of lm function to be used in knitr using the following code (as suggested by @JoshO'Brien):

<<test, code=lm, eval=FALSE>>=
@

But could not figure out how to control the width of knitr output.

---

To embed a 'tidy' definition of some function see Yihui's self-explanatory existing code,

<<insert-fun, echo=FALSE>>=
insert_fun = function(name) {
  read_chunk(lines = capture.output(dump(name, '')), labels = paste(name, 'source', sep = '-'))
}
@

<<insert-lm, echo=FALSE>>=
insert_fun('lm')
@

<<lm-source, eval=FALSE, tidy=TRUE, tidy.opts=list(width.cutoff=30)>>=
@

Example Rnw and Rmd Gist

---

When output is going to latex, there are sometimes have issues with getting line breaks to stay within the page margins. Its a known issue with multiple fixes that have various drawbacks. Like this one where you get the full function within the margins but without the pretty coloring... It is all a matter of trade-offs and/or effort you put into a solution. :)

documentclass{article}

usepackage{listings}
usepackage{inconsolata}

<<echo=FALSE>>=
options(width=60)

listing <- function(x, options) {
  paste("begin{lstlisting}[language=R,basicstyle=ttfamily,breaklines=true]n",
    x, "end{lstlisting}n", sep = "")
}
knit_hooks$set(source=listing, output=listing)

insert_fun = function(name) {
  read_chunk(lines = capture.output(dump(name, '')), labels = paste(name, 'source', sep = '-'))
}

@

<<insert-lm, echo=FALSE>>=
insert_fun('lm')
@

begin{document}

<<lm-source, eval=FALSE, tidy=TRUE, tidy.opts=list(width.cutoff=50)>>=
@

end{document}

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