[Rd] motivation for setRepositories and chooseCRANmirror

[Uwe Ligges]

Jeffrey Horner wrote:

> I have some questions and observations about these:
> 
> Will these replace manually setting options(CRAN), which doesn't work in 
> R-2.1.0?
> 
> In R-2.1.0, setRepositories() looks to see if options("repos") contains 
> a CRAN entry and will not override that CRAN entry even if the 
> $R_HOME/etc/repositories file (which setRepositories reads from) 
> contains a  CRAN entry.  Why is this? The user could easily set 
> options("repos") without the help of this function anyway? And 
> chooseCRANmirror() obviously sets the CRAN entry correctly.
> 
> I've checked the latest nightly tarball, R-devel_2005-06-15.tar.gz, and 
> this observations persists.
> 
> I also observe that the R-2.1.0 Rprofile in the base package sets 
> options(repos=c(CRAN="@CRAN@")), so it seems that the only way to set 
> the CRAN repository entry is either with chooseCRANmirror() or manually 
> setting options("repos") or options("CRAN"). If this was not the case, 
> then setRepositories() would choose the CRAN entry from 
> $R_HOME/etc/repositories.
> 
> In R-2.1.0 and in R-devel_2005-06-15.tar.gz, the R-admin manual suggests 
> that for packages to be downloaded and installed within R should set 
> options(CRAN = "http://cran.us.r-project.org/"). Will this be changed to 
> calling chooseCRANmirror()?
> 
>  From an administrator's point of view, I would like to have the CRAN 
> option set automatically on R startup for ALL users. That way I don't 
> have to set this option before calling update.packages().
> 
> 


Hence, I have in our department's R installation's 
.../R/etc/Rprofile.site file (which is intended for configurations that 
apply to all users):

options(repos = c(
           CRAN = "http://umfragen.sowi.uni-mainz.de/CRAN",
           CRANextra = "http://www.stats.ox.ac.uk/pub/RWin"))


Uwe Ligges