wrapping figure with latex environment in knitr/rmarkdown with hooks - r

Question

I'd like to wrap figures created with knitr and rmarkdown in a "wrapfigure" environment using hooks. However, when running the minimal example below, the figure chunk only gets compiled into a markdown picture:
\begin{wrapfigure}{R}{0.3\textwidth}
![](test_files/figure-latex/unnamed-chunk-2-1.pdf)
\end{wrapfigure}
and not the expected:
\begin{wrapfigure}{R}{0.3\textwidth}
\includegraphics{test_files/figure-latex/unnamed-chunk-2-1.pdf}
\end{wrapfigure}
Minimal example:
---
header-includes:
- \usepackage{wrapfig}
output:
pdf_document:
keep_tex: TRUE
---
```{r}
library(knitr)
knit_hooks$set(wrapf = function(before, options, envir) {
if(before) {
"\\begin{wrapfigure}{R}{0.3\\textwidth}"
} else {
"\\end{wrapfigure}"
}
})
```
```{r, wrapf=TRUE}
library(ggplot2)
qplot(cars$speed, cars$dist)
```

Answer 1

pandoc is responsible for converting the markdown document to a TEX document. As pandoc doesn't touch between \begin{…} and \end{…} the markdown syntax for the image is not being converted to TEX syntax.
You could …
Hide the plot (fig.show = 'hide') and use something along the lines of cat("\includegraphics{figure/unnamed-chunk-2-1.pdf}").
Hide the plot as above and include some magic in the hook that saves the cat.
Write RNW instead of RMD if you want PDF output.
Here's an example for option 2:
knit_hooks$set(wrapf = function(before, options, envir) {
if(before) {
return("\\begin{wrapfigure}{R}{0.3\\textwidth}")
} else {
output <- vector(mode = "character", length = options$fig.num + 1)
for (i in 1:options$fig.num) {
output[i] <- sprintf("\\includegraphics{%s}", fig_path(number = i))
}
output[i+1] <- "\\end{wrapfigure}"
return(paste(output, collapse = ""))
}
})
This hook can be used with wrapf = TRUE and fig.show = "hide". (Moreover, you need to add \usepackage{graphics} to header-includes.)
But note that I would not do it! Too many things can go wrong in more complex settings. Think of cache, captions, labels, cache (again!) …
Therefore, if it is really necessary to control the typesetting of the PDF, I recommend writing RNW (option 3).