Get verbatim R chunks into R Markdown

This article is reposted from a gist with the kind permission of Jenny Bryan.

My periodic revisitation of “how can I include a verbatim R chunk in .rmd”? This time I am writing it down! Various proposed solutions:

From the knitr FAQ:

`r ''` ```{r label, what=ever}

 ```{r label, what=ever}

From issue 443

`r ''````{r foo}
print('hello world!')
```

```{r foo}
print('hello world!')
```

From knitr example 065, involving inline R code:

```{r eval=TRUE}`r ''`
n = 10
rnorm(x)
```

```{r eval=TRUE}
n = 10
rnorm(x)
```

Also from knitr example 065, involving a zero-width space (copy and paste the input code into the RStudio editor to see the zero-width space after the first back tick):

```{r eval=TRUE}
n = 10
rnorm(n)
```

```{r eval=TRUE}
n = 10
rnorm(n)
```

From Karl Broman, involving <pre> and <code> tags:

<pre><code>```{r whatever}
data(cars)
summary(cars)
```</code></pre>

```{r whatever}
data(cars)
summary(cars)
```