R functions for saving the list of installed packages and then reinstalling them all when you upgrade R

save-restore-pkgs.R

savepkgs <- function(saveloc)
{
    instpkg <- installed.packages()
    cranpkg <- available.packages()
    iscran <- instpkg[,'Package'] %in% cranpkg[,'Package']
    pkgdata <- data.frame(package=instpkg[,'Package'], iscran=iscran, instvers=instpkg[,'Version'])
    write.csv(pkgdata, saveloc)
}

restore_pkgs <- function(pkglistfile)
{
    pkgtbl <- read.csv(pkglistfile, stringsAsFactors = FALSE)
    pkglist <- pkgtbl$package[pkgtbl$iscran]
    ## install the packages we can get from CRAN
    install.packages(pkglist, dependencies=TRUE, type='source', Ncpus=8)
    ## Message about the ones we can't get from CRAN
    nocran <- pkgtbl$package[!pkgtbl$iscran]
    nocranstr <- paste(nocran, collapse=', ')
    message('The following packages were not available from CRAN: ', nocranstr)
    ## Return the list of not-installed packages for the user's consideration
    nocran
}