[R] knitr and stopifnot replacement.

Yihui Xie xie at yihui.name
Fri Aug 22 17:42:59 CEST 2014

Yep, that is exactly the answer.

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

On Fri, Aug 22, 2014 at 6:35 AM, Bart Kastermans <kasterma at kasterma.net> wrote:
> On 22 Aug 2014, at 12:39, Duncan Murdoch <murdoch.duncan at gmail.com> wrote:
>> On 22/08/2014, 6:02 AM, Bart Kastermans wrote:
>>> I have a daily generated report in which I put a check using stopifnot.  Unfortunately
>>> I didn’t check the effect very well, turns out that if the condition checked fails
>>> this is not shown in the knitr output (I only get an error much later due to a missing
>>> object).
>>> So my question is, what is the correct way to use assertions in a <filename>.Rnw
>>> file.  I want to perform a check, and if it fails everything should stop with a message
>>> I can generate.
>> One of the differences between knitr and Sweave is that knitr handles
>> errors, and Sweave doesn't.  I expect there's some knitr option to tell
>> it to quit in case of error (a hook?), but you'll have to check the
>> documentation to find it.
> Thanks; that helped me to find the exact right option:
> <<filelist, error=FALSE>>=
> # check all files exist before continuing
> stopifnot(all(sapply(files, file.exists)))
> @

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