knitr - Conditionally display a block of text in R Markdown

Question

I am using knitr to parse an R Markdown document . Is there a way to conditionally display a block of text in R Markdown depending on a variable in the environment I pass into knitr?

For instance, something like:

`r if(show.text) {`
  la la la
`r }`

Would print "la la la" in the resulting doc if show.text is true.

Answer 1

You need a complete R expression, so you cannot break it into multiple blocks like you show, but if the results of a block are a text string then it will be included as is (without quotes), so you should be able to do something like:

`r if(show.text){"la la la"}`

and it will include the text if and only if show.text is TRUE.