Embed Rmarkdown with Rmarkdown, without knitr evaluation

Question

I want to demonstrate how to write RMarkdown, where said RMarkdown demonstration is embedded within an RMarkdown document used to create the course material. Within this fenced code block, I don't want knitr to execute the chunk.

I want to put something like this into my "top level" Rmarkdown document, and have everything that's between the outer fences be printed verbatim in fixed width in the output HTML document, rather than having knitr evaluate the inner embedded R code chunk and inline code.

```
---
title: "RMarkdown teaching demo"
author: "whoever"
---

# Major heading

Here's some text in your RMarkdown document. Here's a code chunk:

```{r, eval=FALSE}
head(mtcars)
```

Now we're back into regular markdown in our embedded document.

Here's inline code that I don't want executed either; 
e.g. mean of mpg is `r mean(mtcars$mpg)`.

```

I've tried the zero-width space trick in knitr example 65, but this fails when trying to compile to PDF (I need both HTML and PDF).

Answer 1

Here is one way to achieve it. You may add `r ''` before the chunk header so that the code chunk is not recognized, and use knitr::inline_expr() to generate `r `.

````
---
title: "RMarkdown teaching demo"
author: "whoever"
---

# Major heading

Here's some text in your RMarkdown document. Here's a code chunk:

`r ''````{r, eval=FALSE}
head(mtcars)
```

Now we're back into regular markdown in our embedded document.

Here's inline code that I don't want executed either; 
e.g. mean of mpg is `r knitr::inline_expr('mean(mtcars$mpg)')`.

````

It will be easier if you just save the R Markdown example document in a separate file, and include it in the top-level document via readLines(), e.g.

````
`r paste(readLines('example.Rmd'), collapse = '\n')`
````

To include three backticks in a fenced code block, you need more than three backticks. That is why I'm using four here.

Answer 2

I do this using the cat function, which works for both HTML and PDF output.

---
title: "RMarkdown teaching demo"
author: "whoever"
---

# Major heading

Here's some text in your R Markdown document. Here's a code chunk:

```{r, echo=FALSE, comment=""}
cat(c("```{r, eval=FALSE}",
      "head(mtcars)",
      "```"), 
    sep='\n')
```

Now we're back into regular Markdown in our embedded document.

Here's inline code that I don't want executed either: 

```{r, echo=FALSE, comment=""}
cat("The mean of mpg is `r mean(mtcars$mpg)`.")
```