[R] Having two different versions of a package in the same R installation

[Gabor Grothendieck]

On Tue, Oct 2, 2012 at 4:18 PM, Søren Højsgaard <sorenh at math.aau.dk> wrote:
> Dear list,
>
> I am making some comparisons of two versions of the lme4 package: The CRAN version and the R-Forge version. For the moment I have two different R installations, each with a different version of lme4. However it would be convenient if I could have the same version within the same R installation such that I can run a code chunk on one lme4 version and immediately after run the same code chunk on another lme4 version. Does anyone know if this is possible?
>

Install the two versions into two different R libraries:

install.packages("my.package", repos = ..., lib = ...) # 1st repo/lib
install.packages("my.package", repos = ..., lib = ...) # 2nd repo/lib

library(my.package, lib.loc = ...) # 1st lib
# use it
detach(my.package, unload = TRUE)
# next line may or may not be needed
library.dynam.unload("my.package", system.file(package = "my.package"))
library(my.package, lib.loc = ...) # 2nd lib

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