Using texPreview Built-in Knitr Engine

texPreview contains inside its own knitr engine to render TeX snippets more naturally within the RMarkdown workflow. We achieve this by leveraging texPreview’s integration via S3 for various classes.

The following inputs can be run inside texpreview chunks in RStudio version 1.2.5033 and above. They will render in the same fashion as would a regular texPreview::tex_preview call.

• Raw TeX
• TeX in a character vector
• knitr_kable (kable/kableExtra)
• xtable
• texreg
• equatiomatic

Arguments that were used in the texPreview::tex_preview function are now set in the chunk options. To make them unique to this engine we prefix them with texpreview, below is a table with the chunk options and their tex_preview analogue.

tex_preview argument	chunk option	default value
returnType	texpreview.return	‘engine’
fileDir	texpreview.path	tex_opts$get(‘fileDir’)
stem	texpreview.stem	‘tex_temp’

The user still has the option to use texPreview::tex_opts to control chunk outputs as they are passed into the call internally. The chunk options will override any settings that are in texPreview::tex_opts.

Rendering the chunk interactively will have different side effects depending on the texpreview.return setting. These settings have the same side effects as the returnType settings with one addition ‘engine’ which mimics returnType=‘viewer’. It should be the preferred settings when working with RMarkdown documents that return HTML outputs.

The following are examples of some uses of the texpreview engine.

library(texPreview)
dir.create('images/engine',showWarnings = FALSE)

Default

Chunk Call

Output

knitr::kable(head(iris),format = 'latex',booktabs = TRUE)

No Echo

The texpreview engine respects regular ‘r’ engine chunk options such as ‘echo’:

Chunk Call

Output

Raw TeX Table

Chunk Call

```texpreview
\begin{tabular}{llr}
\hline
\multicolumn{2}{c}{Item} \\
\cline{1-2}
Animal    & Description & Price (\$) \\
\hline
Gnat      & per gram    & 13.65      \\
          & each        & 0.01       \\
Gnu       & stuffed     & 92.50      \\
Emu       & stuffed     & 33.33      \\
Armadillo & frozen      & 8.99       \\
\hline
\end{tabular}
```

Output

\begin{tabular}{llr}
\hline
\multicolumn{2}{c}{Item} \\
\cline{1-2}
Animal    & Description & Price (\$) \\
\hline
Gnat      & per gram    & 13.65      \\
          & each        & 0.01       \\
Gnu       & stuffed     & 92.50      \\
Emu       & stuffed     & 33.33      \\
Armadillo & frozen      & 8.99       \\
\hline
\end{tabular}

Output Path

Chunk Call

Output

list.files('images/engine')
#> [1] "example.png"           "example.tex"           "unnamed-chunk-2-1.png"
#> [4] "unnamed-chunk-3-3.png" "unnamed-chunk-4-5.png" "unnamed-chunk-5-7.png"

PDF Documents

Setting texpreview.return = ‘input’ will have the chunk return an LateX ‘input’ call with the results ‘asis’ so the user can render the lines as part of a Rmarkdown pdf document.

```texpreview
knitr::kable(head(iris),format = 'latex',booktabs = TRUE)
```
\input{images/engine/example.tex}

Setting texpreview.return = ‘tex’ will have the chunk return the tex lines output with the results ‘asis’ so the user can render the lines as part of a Rmarkdown pdf document.

```texpreview
knitr::kable(head(iris),format = 'latex',booktabs = TRUE)
```

\resizebox{\textwidth}{!}{
\begin{tabular}{rrrrl}
\toprule
Sepal.Length & Sepal.Width & Petal.Length & Petal.Width & Species\\
\midrule
5.1 & 3.5 & 1.4 & 0.2 & setosa\\
4.9 & 3.0 & 1.4 & 0.2 & setosa\\
4.7 & 3.2 & 1.3 & 0.2 & setosa\\
4.6 & 3.1 & 1.5 & 0.2 & setosa\\
5.0 & 3.6 & 1.4 & 0.2 & setosa\\
\addlinespace
5.4 & 3.9 & 1.7 & 0.4 & setosa\\
\bottomrule
\end{tabular}
}