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  #           File Name              :  transferLibrary.R                                                                      #
  #           Last Updated Funclist  :  08 Feb 2015,  5:12 AM (Sunday)                                                         #
  #                                                                                                                            #
  #           Author Name            :  Rick Saporta                                                                           #
  #           Author Email           :  RickSaporta@gmail.com                                                                  #
  #           Author URL             :  www.github.com/rsaporta                                                                #
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  #           Packages Called        :  NA                                                                                     #
  #           Packages Used via NS   :  NA                                                                                     #
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  #   txrL.Out <- transferLibrary.Out ( dir="~/git/misc/!SysAdmin", fileName="pkglist.Rdata", createIfMissing=TRUE, dx=TRUE )  #
  #   txrL.In <- transferLibrary.In   ( dir="~/git/misc/!SysAdmin", fileName="pkglist.Rdata", dep=FALSE, update=TRUE           #
  #                                     , dx=TRUE )                                                                            #
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  #                                                     <END FUNCS>                                                            #
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# Used to transfer all installed packages from one system to another.  
#  Note:  Systems must have similar OS's.   eg: cannot go from OS X to Ubuntu 


# These two functions are implementations of @DWin's suggestions on StackOverflow
#  http://stackoverflow.com/questions/7133394/migrating-r-libraries

txrL.Out <- transferLibrary.Out <- function(dir="~/git/misc/!SysAdmin", fileName="pkglist.Rdata", createIfMissing=TRUE, dx=TRUE) {
# depends on as.path()
#
# Arguments:  dx: use dropbox dir
  
  if (dx)
    dir <- "~/Dropbox/tmp" 

  dir <- path.expand(dir)

  # Check that dir exists
  if (createIfMissing) {    
    dir.create(dir, showWarnings=FALSE)
  }  else {
    if (!file.exists(dir))
      stop(dir, " NOT FOUND")
  }
 
  # in installed.packages(), the Priority column alludes to which packages come installed. 
  # Therefore, we want those with no specified priority. 
  # .... I"m not positive that this is true.  
  # We might be better off excluding priorities c("base", "recommended") 
  #   as I'm not sure if there are other ways for a package to have a different priority


  # Note: the name of object `save.pkg.list` must match with that of `transferLibrary.In`
  save.pkg.list <- installed.packages()[is.na(installed.packages()[ , "Priority"]), 1]
  save(save.pkg.list, file=as.path(dir, fileName))
}


txrL.In <-  transferLibrary.In <- function(dir="~/git/misc/!SysAdmin", fileName="pkglist.Rdata", dep=FALSE, update=TRUE, dx=TRUE) {
# depends on as.path()
# 
# Arguments:   dep:  If TRUE will also install dependencies. 
#           update:  If TRUE will run update.packages() after installation completes.
#               dx:  If TRUE will over-right the value in dir with a dropbox dir.

  if (dx)
    dir <- "~/Dropbox/tmp" 

  file <- as.path(dir, fileName)

  # Check that file exists
  if (!file.exists(file))
      stop(dir, " NOT FOUND")
  
  # load in the list of packages
  load(as.path(dir, "pkglist.Rdata"))

  # Install the packages
  # Note: the name of object `save.pkg.list` must match with that of `transferLibrary.Out`  
  install.packages(save.pkg.list, dependencies=dep)

  # update all packages, if flagged (TRUE by default)
  if (update)
    update.packages(checkBuilt=TRUE)
}