how to add a (multipage) pdf to rmarkdown?

Question

Consider this simple example

library(dplyr)
library(ggplot2)
library(tidyr)

mydata <- data_frame(group = c('a', 'a', 'a', 'b', 'b', 'b'),
                     x = c(1,2,3,5,6,7),
                     y = c(3,5,6,4,3,2))

mydata2 <- mydata %>% group_by(group) %>% 
  nest() %>% 
  mutate(myplot = map(data, ~ggplot(data = .x, aes(x = x, y = x)) + geom_point()))

pdf("P://mychart.pdf")
print(mydata2$myplot)
dev.off()

The code above will output a pdf with two pages. How can I show these two pages on my rmarkdown document?

Using

---
title: "crazy test"
output:
  pdf_document
---

```{r global_options, include=FALSE}
knitr::opts_chunk$set(echo = TRUE, fig.pos = 'h')
```


ttt

## this is a test!!

```{r label, out.width = "85%", fig.cap = "caption"}
knitr::include_graphics(path = "P://mychart.pdf")
```

will only show the first page of the pdf! Where is the other chart? :(

Any ideas?

Thanks!

Answer 1

One can use pdfpages to include multiple pages from a PDF file at once. However, these are included on separate pages. While it is possible to add page numbers, you cannot easily put these images into a figure environment. Fortunately, \includegraphics has an option to use individual pages from a PDF. Unfortunately, knitr::include_graphics does not allow passing additional arguments to \includegraphics.

Here both possibilities:

---
title: "crazy test"
output:
  pdf_document
header-includes:
  - \usepackage{pdfpages}
---

```{r global_options, include=FALSE}
knitr::opts_chunk$set(echo = TRUE, fig.pos = 'h')
```


```{r, include=FALSE}
library(dplyr)
library(ggplot2)
library(tidyr)
library(purrr)

mydata <- data_frame(group = c('a', 'a', 'a', 'b', 'b', 'b'),
                     x = c(1,2,3,5,6,7),
                     y = c(3,5,6,4,3,2))

mydata2 <- mydata %>% group_by(group) %>% 
  nest() %>% 
  mutate(myplot = map(data, ~ggplot(data = .x, aes(x = x, y = x)) + geom_point()))

pdf("mychart.pdf")
print(mydata2$myplot)
dev.off()
```


## this is a test!!

Only first page

```{r label, out.width = "85%", fig.cap = "caption"}
knitr::include_graphics(path = "mychart.pdf")
```

All pages but w/o caption and taking a full page

\includepdf[pages=-,nup=2,pagecommand={}]{mychart.pdf}

Alternative, using explicit LaTeX commands.

\begin{figure}
\includegraphics[page=1,width=0.5\linewidth]{mychart.pdf}
\includegraphics[page=2,width=0.5\linewidth]{mychart.pdf}
\caption{\label{fig:test} Test.}
\end{figure}

One could also put these into a R chunk with cat() and result = 'asis'. However, the options for setting caption etc. are still not used.