058-engine-tikz.Rmd

# TikZ graphics

## Description

The engine inserts the code into a latex-string-template, which is then processed by LaTeX (and the **magick** package if `fig.ext` is not `pdf`).

## Options

You can pass some options to the engine by defining `engine.opts`, e.g. use your own template instead of the default one to include the tikz code: `engine.opts = list(template = "mytemplate.tex")`. The default template can be found under `system.file('misc', 'tikz2pdf.tex', package = 'knitr')`.

## Example

An example of the tikz-engine from <https://raw.github.com/sdiehl/cats/master/misc/example.md>

```{tikz, tikz-ex, fig.cap = "Funky tikz", fig.ext = 'png', cache=TRUE}
\usetikzlibrary{arrows}
\begin{tikzpicture}[node distance=2cm, auto,>=latex', thick, scale = 0.5]
\node (P) {$P$};
\node (B) [right of=P] {$B$};
\node (A) [below of=P] {$A$};
\node (C) [below of=B] {$C$};
\node (P1) [node distance=1.4cm, left of=P, above of=P] {$\hat{P}$};
\draw[->] (P) to node {$f$} (B);
\draw[->] (P) to node [swap] {$g$} (A);
\draw[->] (A) to node [swap] {$f$} (C);
\draw[->] (B) to node {$g$} (C);
\draw[->, bend right] (P1) to node [swap] {$\hat{g}$} (A);
\draw[->, bend left] (P1) to node {$\hat{f}$} (B);
\draw[->, dashed] (P1) to node {$k$} (P);
\end{tikzpicture}
```

## Tips

To develop the tikz-code, you could use `qtikz` or `ktikz`.