[R] [Rd] How to link to vignette from .Rd file

[Agner Fog]

Duncan Murdoch wrote:

> Actually how you built the .pdf is irrelevant, but it does look for 
> file with the same name and one of these extensions:
>
>  "Rnw"  "rnw"  "Snw"  "snw"  "Rtex" "rtex" "Stex" "stex"
>
> So you could just create a zero length file with the same basename and 
> one of those extensions, and it should work.
>
> I don't know if this restriction is intentional.

I wouldn't rely on this hack working in future versions. What if it 
creates an empty pdf file from the zero-length Rnw file or deletes the 
pdf file for the reason that the Rnw file is invalid. It is better to 
make the system recognize pdf files than to rely on dirty undocumented 
hacks, IMHO.