how to include pdfpages in rmarkdown for beamer output - latex

Question

I am creating pdf slides using rmarkdown and beamer. When using latex instead of rmarkdown, I can include arbitrary pages from pdf files into my slides with
\usepackage{pdfpages}
...
\includepdf[pages={1-10}]{another_file.pdf}
Is it possible to achieve this with rmarkdown? Note that when just issuing the \includepdf command, intended to be located between slides, pandoc wraps it between \begin{frame} and \end{frame}.

Answer 1

Not a perfect solution but it works (adapted from https://tex.stackexchange.com/questions/11458/error-when-inserting-a-pdf-page-into-a-beamer-presentation?newreg=10fd6a4a46c642118eb4ec905cf87303): use \includegraphics instead of includepdf. This works inside of frames but you have to manyally create a frame for each page you want to insert as it only allows to insert a single page at time.
---
title: "Foo"
output:
beamer_presentation:
---
# Stolen image
---
\includegraphics[page=1,width=\paperwidth]{lecture-1-terminal.pdf}
# My own work
## My slide 1
Great stuff!

Answer 2

In rmarkdown you can use pdfpages like this:
---
output:
beamer_presentation:
keep_tex: true
header-includes:
- \usepackage{pdfpages}
- \setbeamercolor{background canvas}{bg=}
- \makeatletter\beamer#ignorenonframefalse\makeatother
---
test
``` {=latex}
\end{frame}
\includepdf[pages=1-10]{example-image-duck}
\begin{frame}
```
test
(the line \setbeamercolor{background canvas}{bg=} is necessary for beamer versions < 3.64, a patch has been added in 9e3bb9)

Answer 3

As you mentioned, you can inlcude raw TeX in Pandoc Markdown. For me the following works:
$ pandoc -t beamer
foo
\includepdf[pages={1-10}]{another_file.pdf}
bar
^D
which results in:
\begin{frame}
foo
\includepdf[pages={1-10}]{another_file.pdf}
bar
\end{frame}
Maybe you need to update your pandoc version? (I'm currenlty using 2.0 from pandoc nightlies)