[R] conditionally disable evaluation of chunks in Rmarkdown...

Yihui Xie xie at yihui.name
Tue Nov 10 18:00:53 CET 2015

The short answer is you cannot. Inline R code is always evaluated.
When it is not evaluated, I doubt if your output still makes sense,
e.g. "The value of x is `r x`." becomes "The value of x is ." That
sounds odd to me.

If you want to disable the evaluate of inline code anyway, you may use
a custom function to do it. e.g.

cond_eval = function(x) {
  if (isTRUE(knitr::opts_chunk$get('eval'))) x

Then `r cond_eval(x)` instead of `r x`.

Yihui Xie <xieyihui at gmail.com>
Web: http://yihui.name

On Tue, Nov 10, 2015 at 4:40 AM, Witold E Wolski <wewolski at gmail.com> wrote:
> I do have an Rmd where I would like to conditionally evaluate the second part.
> So far I am working with :
> ```{r}
> if(length(specLibrary at ionlibrary) ==0){
>   library(knitr)
>   opts_chunk$set(eval=FALSE, message=FALSE, echo=FALSE)
> }
> ```
> Which disables the evaluation of subsequent chunks.
> However my RMD file contains also these kind of snippets : `r `
> How do I disable them?
> regards
> --
> Witold Eryk Wolski

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