Reusing code chunks from an existing Rmarkdown document

example.Rmd

This code chunk will extract all code blocks from `example.Rmd` and write them to a temporary file, preservining chunk options. It will then read them and make those chunks avaliable in the current R environment when the presentation is knitted.

```{r include, eval=TRUE, echo=FALSE, include = FALSE}
tmp_script <- tempfile()
knitr::purl("example.Rmd", output=tmp_script, quiet = TRUE)
knitr::read_chunk(tmp_script)
```

We can then include a chunk from `example.Rmd` like so:

```{r chunk-in-report, eval=TRUE, echo=FALSE}
```