R markdown file: include help information - r

Question

I would like to include at the end of the R markdown documention the help page about the mtcars dataset.
In my file I included the following:
```{r}
?mtcars
```
When I compile the markdown (output is to PDF - knitr), upon processing this instruction the help page comes up in my browser but the resulting pdf lacks this section.
Is there a way I could acheive this other then copying from one place to the other?
Thank you.

Answer 1

We can adapt Yihui Xie's static_help function to get the html source for a given help file
static_help <- function(pkg, topic, out, links = tools::findHTMLlinks()) {
pkgRdDB = tools:::fetchRdDB(file.path(find.package(pkg), 'help', pkg))
force(links)
tools::Rd2HTML(pkgRdDB[[topic]], out, package = pkg,
Links = links, no_links = is.null(links))
}
If we write the source to a temporary file we can then read it back in and strip off the header and footer, giving you the body of the help file to include in your markdown document
```{r, echo = FALSE, results = "asis"}
static_help <- function(pkg, topic, out, links = tools::findHTMLlinks()) {
pkgRdDB = tools:::fetchRdDB(file.path(find.package(pkg), 'help', pkg))
force(links)
tools::Rd2HTML(pkgRdDB[[topic]], out, package = pkg,
Links = links, no_links = is.null(links))
}
tmp <- tempfile()
static_help("datasets", "mtcars", tmp)
out <- readLines(tmp)
headfoot <- grep("body", out)
cat(out[(headfoot[1] + 1):(headfoot[2] - 1)], sep = "\n")
```
EDIT
The above solution produced HTML output, whereas the question actually asked for PDF output. We can adapt the above to return latex output instead; this time the only-post-editing required is to switch % for \n
```{r, echo = FALSE, results = "asis"}
static_help <- function(pkg, topic, out, links = tools::findHTMLlinks()) {
pkgRdDB = tools:::fetchRdDB(file.path(find.package(pkg), 'help', pkg))
force(links)
tools::Rd2latex(pkgRdDB[[topic]], out, package = pkg,
Links = links, no_links = is.null(links))
}
tmp <- tempfile()
static_help("datasets", "mtcars", tmp)
out <- readLines(tmp)
out <- gsub("%", "\n", out, fixed = TRUE)
cat(out, sep = "\n")
```
However the .Rd files depend on Rd.sty. The simplest way to get LaTeX to find Rd.sty is to put a copy in the same directory as your .Rmd file. Then you need to define a custom template to replace the default pandoc LaTeX template. Again, the simplest solution is to put a copy of the default template in the same directory as your .Rmd file, then modify it by replacing everything between the \documentclass command and the \begin{document} command (lines 2 - 145) with the command
\usepackage{Rd}
Finally modify the metadata of your .Rmd file to use the new template
---
output:
pdf_document:
template: template.tex
---