how to control which version of a package library() installs?

On Fri, 13 Apr 2007, Tony Plate wrote:

library() seems to remember the location of a package when I give it a
lib.loc, and then use that version thereafter, even if I don't supply

Not quite: it notices that it is loaded and does not load it again, 
possibly attaching the exports of a still-loaded namespace.

lib.loc again.  Is there any way I can load different versions of a
package in one R session? -- I don't seem to able to simply detach the
package and then load a different version from a different library 
location.

Without the output of search(), searchpath() and loadedNamespace() we 
cannot know what happened here.  But here is an example of my own

library(Matrix, lib.loc="~/R/test26")

Loading required package: lattice

searchpaths()

 [1] ".GlobalEnv"
 [2] "/data/gannet/ripley/R/test26/Matrix"
 ...

detach(2)
search()

 [1] ".GlobalEnv"        "package:lattice"   "package:stats"
 [4] "package:graphics"  "package:grDevices" "package:utils"
 [7] "package:datasets"  "package:methods"   "Autoloads"
[10] "package:base"

library(Matrix, lib.loc="~/R/test-library")
searchpaths()

 [1] ".GlobalEnv"
 [2] "/data/gannet/ripley/R/test26/Matrix"
 ...

The point is that the namespace Matrix is still loaded.

detach(2)
unloadNamespace("Matrix")
library(Matrix, lib.loc="~/R/test-library")
searchpaths()

 [1] ".GlobalEnv"
 [2] "/data/gannet/ripley/R/test-library/Matrix"

Might your example be similar?

$ R
[...startup info...]

# only version we currently know about is in the standard library
.find.package("ExamplePackage")

[1] "c:/R/R-2.4.1/library/ExamplePackage"

# load a version from a different library e:/devinst
library(ExamplePackage, lib.loc="e:/devinst")
# and check we've got the right version ... yes
system.file(package="ExamplePackage")

[1] "e:/devinst/ExamplePackage"

.find.package("ExamplePackage")

[1] "e:/devinst/ExamplePackage"

detach(2)

# Now I'd like to load the version in the standard library.
# .find.package() finds the version I want
.find.package("ExamplePackage")

[1] "c:/R/R-2.4.1/library/ExamplePackage"

# but library() loads the same version it did before, even
# though I don't supply lib.loc, and .libPaths is untouched.
library(ExamplePackage)
system.file(package="ExamplePackage")

[1] "e:/devinst/ExamplePackage"

.find.package("ExamplePackage")

[1] "e:/devinst/ExamplePackage"

.libPaths()

[1] "c:/R/R-2.4.1/library"

sessionInfo()

R version 2.4.1 (2006-12-18)
i386-pc-mingw32

locale:
LC_COLLATE=English_United States.1252;LC_CTYPE=English_United
States.1252;LC_MON
ETARY=English_United States.1252;LC_NUMERIC=C;LC_TIME=English_United
States.1252


attached base packages:
[1] "stats"     "graphics"  "grDevices" "utils"     "datasets"  "methods"
[7] "base"

other attached packages:
ExamplePackage
         "1.0"

Am I doing something wrong here?  I can't find any mention of
persistence of package location in ?library.

thanks for any help or suggestions,

Tony Plate