Commenting in rmarkdown/knitr to prevent R evaluation
knitr, r, r-markdown
Solution
As @NicE said, `knitr` goes first to evaluate your code, in particular because there may be inline R code evaluation or other R variable dependent text, which then need to be evaluated as markdown syntax. For instance, this included in rmarkdown:
Define if bold `r bold <- TRUE`
This text is `r ifelse(bold, "**bold**", "_italic_")`.
Gives:
Define if bold This text is bold.
Then, I think the only way to insert comments without evaluating them is to embed them in a chunk with `eval=FALSE` & `echo=FALSE`
{r, eval=FALSE, echo=FALSE} So when I say that `x` is `r x` in the text, I'd like to comment it out
`
Problem
The recommendation for commenting in `.Rmd` documents to use HTML commenting `<!-- comment here -->` is insufficient. I'd like to comment out a section of my document that includes inline evaluations: ``` I haven't defined `x` yet. <!-- So when I say that `x` is `r x` in the text, I'd like to comment it out --> ``` Knitting this fails: ``` # |.................................................................| 100% # inline R code fragments # # # # # processing file: test.Rmd # Quitting from lines 2-3 (test.Rmd) # Error in eval(expr, envir, enclos) : object 'x' not found # Calls: <Anonymous> ... in_dir -> inline_exec -> withVisible -> eval -> eval # Execution halted ``` One option is to comment each inline section: ``` I haven't defined `x` yet. So when I say that `x` is `r #x` in the text, I'd like to comment it out ``` But this suffers if I'd like to comment out a whole paragraph with several such inline calculations, for example. Is there a more canonical way of doing this?