searchable source dirs for R (aka, a "classpath" for R)

mylib.R

## this should get loaded by your ~/.Rprofile
## either just stick all these definitions right in ~/.Rprofile, or
## have ~/.Rprofile source this file, etc.

source.dirs <- c(
  ## add any "base" locations here.  this is like a "classpath" in java
  ## my default is c("~/myRUtils/src","~/companyRUtils/src","~/publicRUtils"),
  ## but you can use whatever you like
  paste(Sys.getenv("HOME"),"myRUtils","src", sep="/"),
  paste(Sys.getenv("HOME"),"companyRUtils","src", sep="/"),
  paste(Sys.getenv("HOME"),"publicRUtils", sep="/")
)

mylib <- function(lib, path=source.dirs, verbose=T){
  ## use this to search for a file in source.dirs (aka, your R "classpath")
  for(p in path) {
    cand = paste(p, lib, sep="/")
    if(file.exists(cand)) {
      if(verbose)
        print(paste("found", cand))
      source(cand)
      return(invisible(cand))
    }
  }
  print(paste("couldn't find ", lib, " in any of : ", path))
  return(invisible(NULL))
}

usage.R

## say I've set my "source.dirs" to 
##   c("~/myRUtils/src","~/companyRUtils/src","~/publicRUtils")

## first, I want to load a "~/companyRUtils/src/io/fileUtils.R".  The idea is, 
## this file is shared inside our company (hopefully in version control).  
## Everyone can load the file the same way, as long as the setup the base part
## of their "classpath" appropriately

mylib("io/fileUtils.R")


## now I want to load one of my scripts that is still a little too hacky to even
## be worth sharing internally, but its still useful to me, so I dropped it in 
## "~/myRUtils/src/plotsUtils.R"

mylib("plotUtils.R")

## finally, I've pulled some assorted R scripts into my "~/publicRUtils" dir -- 
## maybe even from github.  I can easily load them up as well.  Note that 
## "~/publicRUtils is *last* in my `source.dir`, so it if there is another file 
## with this name in "~/myRUtils/src" or "~/companyRUtils/src", that would get
## used instead

mylib("somebodysAwesomeHelperFunctionsButThatArentInAPackage.R")