Using tikz graphdrawing library within RMarkdown … Need to use lualatex engine, but can't get it to work

Question

I have the following code in an rmd file which leverages tikz for diagrams:

---
title: \"TestNonTufteLua\"
author: \"Me\"
output:
          


        

Answer 1

Update: Meanwhile knitr no longer uses tools::texi2dvi but tinytex::latexmk. One therefore has to use options(tinytex.engine = 'lualatex') in a set-up chunk.

---

This is rather tricky, since you are not using tikzDevice but the tikz engine, which uses tools::texi2dvi to convert to PDF. You can change this using options(texi2dvi = "lualatex"). However, the default template does not work with LuaLaTeX. I have therefore created a modified template:

\RequirePackage{luatex85}
\documentclass{article}
\usepackage[luatex,active,tightpage]{preview}
\usepackage{amsmath}
\usepackage{tikz}
\usetikzlibrary{matrix}
\begin{document}
\begin{preview}
%% TIKZ_CODE %%
\end{preview}
\end{document}

And specify that file with engine.opts = list(template = "tikz2pdf.tex"). Putting it all together here my working file:

---
title: "TestNonTufteLua"
author: "Me"
output:
  pdf_document :
    latex_engine: lualatex
---

```{r}
options(texi2dvi = "lualatex")
```

```{r tikTest2, eval = TRUE, engine = "tikz", engine.opts = list(template = "tikz2pdf.tex")}
\usetikzlibrary{graphs, graphdrawing}
\usegdlibrary{layered}
\tikz [gr/.style={gray!50}, font=\bfseries]
\graph [layered layout] {
    % A and F are horizontally aligned if you also set weight=0.5 for A -- C.
    A -- [minimum layers=2] C -- F,
    { [nodes=gr, edges=gr] A -- B -- { E, D -- F } }
};
```

Result:

References:

• how to set engine options
• preview and LuaLaTeX
• knitr using texi2pdf

Answer 2

A small running variation of the example above is the following using tinytex.

    ---
    title: "lualatex. Using `tinytex.engine`"
    output:
      html_document:
        df_print: paged
      pdf_document:
        latex_engine: lualatex
    ---

   ## Latex engines
   By default, PDF documents are rendered using `pdflatex`. You can specify an
   alternate engine using the `latex_engine` option. Available engines 
   are `pdflatex`, `xelatex`, and `lualatex.` 

    ```{r setup}
    options(tinytex.engine = "lualatex")
    ```

    ```{r tikzLua, eval = TRUE, engine = "tikz", engine.opts = list(template =  "tikz2pdf.tex")}
    \usetikzlibrary{graphs, graphdrawing}
    \usegdlibrary{layered}

   \tikz [gr/.style={gray!50}, font=\bfseries]
   \graph [layered layout] {
    % A and F are horizontally aligned if you also set weight=0.5 for A -- C.
    A -- [minimum layers=2] C -- F,
    { [nodes=gr, edges=gr] A -- B -- { E, D -- F } }
    };
    ```

After an update in knitr the example above stopped running.