Print marked-up, unevaluated code from another file using Rmarkdown / knitr

print_code.Rmd

---
title: "test"
author: "Richard Smith-Unna"
date: "21 May 2015"
output: html_document
---
 
Demo of reading an R file and dumping it raw into the HTML produced by knitr from RMarkdown, to get syntax highlighting.
 
Put the code you want to display in `import.R`.

Two ways to do it...
 
```{r}
# first load the code
sourcecode <- paste(readLines("import.R"), collapse="\n")
```
 
This block loads the code from an external variable, doesn't evaluate it, and just prints it marked up as though it were a normal block.
```{r eval=FALSE, code=sourcecode}
```

This block prints the code directly to the resulting markdown file, with the code block tags added, using `cat()` to avoid line numbers.
```{r results='asis', echo=FALSE}
cat(paste("```r", sourcecode, "```", sep="\n"))
```