latexr-markdownpandocpdflatex

Formatting Rmd grey box around in line code text in pdf output

When I knit an Rmd doc to HTML, in-line code text shows up as a different font and surrounded by a grey box:

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

Note that the `echo = FALSE` parameter was added to the code chunk to prevent printing of the R code that generated the plot.

enter image description here

If I knit the same document to a pdf instead, the grey box disapears, making it more difficult to distinguish code from regular text:

enter image description here

Is there a way to format the output of in-line code in the pdf outputs?

> sessionInfo()
R version 4.4.0 (2024-04-24 ucrt)
Platform: x86_64-w64-mingw32/x64
Running under: Windows 10 x64 (build 19045)

Matrix products: default


locale:
[1] LC_COLLATE=English_United States.utf8  LC_CTYPE=English_United States.utf8    LC_MONETARY=English_United States.utf8 LC_NUMERIC=C                          
[5] LC_TIME=English_United States.utf8    

time zone: America/Los_Angeles
tzcode source: internal

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base     

other attached packages:
[1] qgraph_1.9.8  igraph_2.0.3  ggplot2_3.5.1 dplyr_1.1.4  

loaded via a namespace (and not attached):
 [1] utf8_1.2.4        generics_0.1.3    gtools_3.9.5      lattice_0.22-6    jpeg_0.1-10       stringi_1.8.4     digest_0.6.35     magrittr_2.0.3   
 [9] evaluate_0.24.0   grid_4.4.0        fastmap_1.2.0     Matrix_1.7-0      plyr_1.8.9        nnet_7.3-19       backports_1.5.0   Formula_1.2-5    
[17] gridExtra_2.3     fansi_1.0.6       scales_1.3.0      pbapply_1.7-2     pbivnorm_0.6.0    abind_1.4-5       mnormt_2.1.1      cli_3.6.2        
[25] rlang_1.1.3       munsell_0.5.1     Hmisc_5.1-3       base64enc_0.1-3   withr_3.0.1       yaml_2.3.8        parallel_4.4.0    tools_4.4.0      
[33] reshape2_1.4.4    checkmate_2.3.2   htmlTable_2.4.3   colorspace_2.1-1  corpcor_1.6.10    fdrtool_1.2.17    vctrs_0.6.5       R6_2.5.1         
[41] png_0.1-8         rpart_4.1.23      stats4_4.4.0      lifecycle_1.0.4   stringr_1.5.1     htmlwidgets_1.6.4 psych_2.4.6.26    foreign_0.8-86   
[49] cluster_2.1.6     glasso_1.11       pkgconfig_2.0.3   pillar_1.9.0      gtable_0.3.5      rsconnect_1.3.1   glue_1.7.0        data.table_1.15.4
[57] Rcpp_1.0.13       xfun_0.44         tibble_3.2.1      tidyselect_1.2.1  rstudioapi_0.16.0 knitr_1.48        farver_2.1.2      nlme_3.1-164     
[65] htmltools_0.5.8.1 lavaan_0.6-18     rmarkdown_2.27    labeling_0.4.3    compiler_4.4.0    quadprog_1.5-8
Solution

  • The echo = FALSE is converted to \texttt{echo = FALSE} in the LaTeX output. You can redefine this command in order to provide the background color box. The light grey from the HTML example is rgba(0, 0, 0, 0.04) which could be translated to #f4f4f4 in Hex. Add

    ```{=latex}
\definecolor{codegray}{HTML}{f4f4f4}
\let\textttOrig\texttt
\renewcommand{\texttt}[1]{\textttOrig{\colorbox{codegray}{#1}}}
```

    at the beginning of your .Rmd and you get something like this in the .pdf:

    enter image description here

    Compared to the .html:

    enter image description here

    Minimal example:

    ---
output: pdf_document
---

```{=latex}
\definecolor{codegray}{HTML}{f4f4f4}
\let\textttOrig\texttt
\renewcommand{\texttt}[1]{\textttOrig{\colorbox{codegray}{#1}}}
```

```{r setup, include=FALSE}
knitr::opts_chunk$set(echo = TRUE)
```

Note that the `echo = FALSE` parameter was added to the code chunk to prevent printing of the R code that generated the plot.