Fixing TeX problems in rmarkdown

If you use rmarkdown to produce pdfs, you may find you have problems with the latest RStudio when printing out LaTeX tables using R packages like xtable or huxtable. Recent versions of pandoc often escape TeX, resulting in errors when you try to compile your PDF.

You can check if this is happening to you by adding keep_tex: yes to your document’s header:

---
...
output:
  pdf_document:
    keep_tex: yes
---

If you then knit the document, it’ll produce the TeX file. If it contains output like:

\textbackslash{}begin\{table\}

where you would expect your table to be, then you have this problem.

The workaround is to add this line to your document’s header:

output:
  pdf_document:
    md_extensions: +raw_attribute

Then, before and after you print out TeX, you can add “raw” blocks to the output. This is a recent extension to pandoc, which ensures that content inside the block is not escaped. Raw attribute blocks look like this in the output.

```{=latex}

% TeX code here...
```

For example, in your Rmarkdown file, you could have a chunk like:

```{r, results = "asis"}
cat("```{=latex}")
xtable(head(mtcars))
cat("```")
```

This will ensure that the TeX produced by xtable gets passed through pandoc, ready to be compiled into a PDF.

You will need pandoc version 2.0.0 or greater to use this trick. You can check your pandoc version using rmarkdown::pandoc_version().

If you use the R huxtable package to produce TeX, version 4.2.1, released yesterday, produces raw attribute blocks automatically in Rmarkdown documents. You will still have to add the +raw_attributes to your document header, though. Hopefully, rmarkdown and/or knitr can find ways to automate this process.