R packages

Library Path Management¶

By default, R searches a set of paths when you request actions involving libraries. The first path is used by default when invoking functions such as install.packages() leading to messages like this:

mkdir: cannot create directory  `/server/linux/lib/R/site-library/00LOCK': Permission denied ERROR: failed to lock directory 

 '/server/linux/lib/R/site-library' for modifying

Fortunately, R provides a number of methods for controlling the library path to accomodate just about any user’s need.

Temporarily changing the library path¶

You can modify R’s notion of your library path on a one-time basis by specifying the lib= argument to install.packages. Suppose there is a directory called MyRlibs in your home directory. The command:

install.packages("caTools",lib="~/MyRlibs")

will install the specified package in your local directory. To access it, the lib.loc= argument of library must be used:

library(caTools,lib="~/MyRlibs")

One problem with this scheme is that if a local library invokes the library() function, it won’t know to also search the local library

Changing the library path for a session¶

The .libPaths() function accepts a character vector naming the libraries which are to be used as a search path. Note that it does not automatically retain directories which are already on the search path. Since the .libPaths() function returns the current search path when called with no arguments, a call like

.libPaths(c("~/MyRlibs",.libPaths()))

will put your local directory at the beginning of the search path. This means that install.packages() will automatically put packages there, and the library() function will find libraries in your local directory without additional arguments.

Permanently changing the library path¶

The environmental variable R_LIBS is set by the script that invokes R, and can be overridden (in a shell startup file, for example) to customize your library path. This variable should be set to a colon-separated string of directories to search. Since it’s always set inside of an R session, the easiest way to get a starting point for it is to use Sys.getenv():

> Sys.getenv("R_LIBS")                          

R_LIBS "/usr/local/linux/lib/R/site-library:/usr/local/lib/R/site-library: /usr/lib/R/site-library:/usr/lib/R/library"

You could then make a copy of this path, modify it, and set the R_LIBS environmental variable to that value in the shell or a startup script.