[Rd] How to avoid function masking

[Roger D. Peng]

I believe recent R-devel has a `pos' argument to library() which lets 
you attach a package in a certain position.  Can't think of anything 
else though.

-roger

Warnes, Gregory R wrote:
> Hi All,
> 
> I've been working on updating the 'genetics' package.  As a consequence of
> the upgrade, .First.lib() looks like:
> 
> 	.First.lib <- function(libname, pkgname) 
> 	{
> 	    if (!require(combinat)) 
> 	        warning("Unable to load 'combinat' library.  Function
> `diseq.ci' will fail.")
> 	    require(gregmisc)
> 	    genotype <- get("genotype",pos="package:genetics")
> 	}
> 
> the First.lib of the "gregmisc" package in turn does 
> 	require("MASS")
> which defines a data set "genotype" which masks the "genotype" function in
> my genetics library.
> 
> Is there any clean way to load libraries in .First.lib while preventing this
> kind of masking?  Ideally, there would be something like
> 
> 	require("gregmisc", top=FALSE)
> 
> which would load the library (and any libraries it loads) into the *third*
> position rather than the second position of the search path (.GlobalEnv is
> in the first slot)?   Actually, does it make sense in general to have
> top=FALSE be  the default behavior when loading packages from .First.lib to
> avoid masking of this type?
> 
> For the moment I'm doing :
> 
> 	.First.lib <- function(libname, pkgname) 
> 	{
> 	    if (!require(combinat)) 
> 	        warning("Unable to load 'combinat' library.  Function
> `diseq.ci' will fail.")
> 	    require(gregmisc)
> 	    assign("genotype", get("genotype",pos="package:genetics"),
> pos=.GlobalEnv )
> 	}
> 
> but this is a hack and doesn't solve the general problem.
> 
> -Greg
> 
> 
> 
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