ifelse action depending on document type in rmarkdown

Question

When preparing reports using rmarkdown: http://rmarkdown.rstudio.com/ one may want the document to render differently depending upon the document type. For ins

Answer 1

Yes, you can access the output format via knitr::opts_knit$get("rmarkdown.pandoc.to"). This will return a string with the target output format. Here's an example:

---
title: "Untitled"
output: html_document
---

```{r}
library(knitr)
opts_knit$get("rmarkdown.pandoc.to")
```

This returns "html" for html_document, "docx" for word_document, and "latex" for pdf_document. So to answer your question you can do something like:

html <- knitr::opts_knit$get("rmarkdown.pandoc.to") == "html"

Answer 2

As pointed out in an answer to a related question, knitr 1.18 introduced the following functions

knitr::is_html_output()
knitr::is_latex_output()

As the name suggests, is_html_output() checks if the output is HTML. You would add something like this to foo.Rmd:

```{r results='asis'}
if (knitr::is_html_output()) {
    cat('<iframe width="640" height="390" src="https://www.youtube.com/embed/FnblmZdTbYs?        feature=player_detailpage" frameborder="0" allowfullscreen></iframe>')
} else {
    cat("https://www.youtube.com/watch?v=ekBJgsfKnlw")
}
```