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).

Densmore

In 2022, knitr introduced the verbatim engine, see here – Midpoint

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.

Humism

That works, only thing I would change is closing the bottom fence the same way, with `r ''````. Otherwise, the syntax highlighting in RStudio gets out of whack. – Densmore

Right. That would help RStudio with syntax highlighting, although it is not necessary for knitr to work. – Humism

For me (rmarkdown_1.0) the inline piece required additional escaping for backticks to appear. – Hippel

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)`.")
```

Herl

Answer 3

Not sure about the pdf output, but surrounding your demo rmarkdown with:

<pre>
...
</pre>

seems to work for html.

Oina

Answer 4

A simple solution that works with R Markdown 2.1 involves using spaces and escape ticks:

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

Note that each line is escaped separately. There are four spaces between the four tick marks and three tick marks. And there are two spaces after the last tick marks on the first and second lines to insert a line break.

Appaloosa

Answer 5

As of 2022-06-16, knitr v1.37, the recommended approach is to use the verbatim engine, ie.

````{verbatim}
```{r}
head(mtcars)
```
````

Midpoint