Change R default library path using .libPaths in Rprofile.site fails to work

Question

I am running R on Windows, not as an administrator. When I install a package, the following command doesn't work:

> install.packages("zoo")
Installing package(s) into ‘C:/Program Files/R/R-2.15.2/library’
(as ‘lib’ is unspecified)
Warning in install.packages :
  'lib = "C:/Program Files/R/R-2.15.2/library"' is not writable

To install a package, I have to specify a library location:

install.packages("zoo", lib="C:/software/Rpackages")

To load a package, I also have to specify the library location:

library("zoo", lib.loc="C:/software/Rpackages")

All of this is OK, but I wanted to see if I could add C:/software/Rpackages to the library path somehow and thus not have to type it each time.

As I searched online, I found that one way to do this is to edit the Rprofile.site file and to add the line

.libPaths("C:/software/Rpackages")

However, after doing this, and starting RStudio, this is the output that I get

> .libPaths()
[1] "C:/Program Files/R/R-2.15.2/library" "C:/Program Files/RStudio/R/library" 

The .libPaths command that I added to the Rprofile.site doesn't seem to have had any effect! Why is this the case? Or more importantly, how can I fix the problem so that I can install and load packages without typing in the library location?

Note: if I start RStudio the .libPaths() command seems to work as it is supposed to

.libPaths("C:/software/Rpackages")
> .libPaths()
[1] "C:/software/Rpackages"               "C:/Program Files/R/R-2.15.2/library"

Isn't that strange?

Answer 1

The proper solution is to set environment variable R_LIBS_USER to the value of the file path to your desired library folder as opposed to getting RStudio to recognize a Rprofile.site file.

To set environment variable R_LIBS_USER in Windows, go to the Control Panel (System Properties -> Advanced system properties -> Environment Variables -> User Variables) to a desired value (the path to your library folder), e.g.

Variable name: R_LIBS_USER 
Variable value: C:/software/Rpackages  

If for some reason you do not have access to the control panel, you can try running rundll32 sysdm.cpl,EditEnvironmentVariables from the command line on Windows and add the environment variable from there.

Setting R_LIBS_USER will ensure that the library shows up first in .libPaths() regardless of starting RStudio directly or by right-clicking an file and "Open With" to start RStudio.

The Rprofile solution can work if RStudio is always started by clicking the RStudio shortcut. In this case, setting the default working directory to the directory that houses your Rprofile will be sufficient. The Rprofile solution does not work when clicking on a file to start RStudio because that changes the working directory away from the default working directory.