Whenever I buy a new computer or format an old one, I have the problem of reinstalling my R packages. If you are a heavy user, you will likely have a significant amount of packages used by your scripts. When you try to run a script in a fresh install of R, it will tell you that you don’t have the proper packages installed. Needless to say that manually installing them is boring.

I’ve found a very simple solution to this problem. I wrote a function that takes as input a folder in the computer and searches for all .R and .Rmd files in all subfolders. It then reads each one and finds all occurrences of library(pkgnamehere) and require(pkgnamehere). It proceeds by checking if the package is locally available and, if not, installs it from CRAN. I’m not sure if this is a new solution but, if you find it interesting and worthy of a CRAN package, let me know in the comment sections. I’m sure I can significantly improve it.

So, whenever I have a fresh computer, I just run the following script:

#install.packages('stringr')

#folder.in <- 'C:/Dropbox/' # windows
folder.in <- '/home/msperlin/Dropbox' # linux 

reinstall.pkgs(folder.in)

and all necessary packages are installed. The needed functions are given next:

reinstall.pkgs <- function(folder.in) {
  my.pattern <- '\\.R$|\\.Rmd'
  
  target.files <- list.files(path = folder.in, pattern = my.pattern  , recursive = T, full.names = T)
  
  all.pkgs <- unlist(sapply(X = target.files, FUN = find.pkgs, USE.NAMES = F))
  all.pkgs <- unique(all.pkgs)
  
  out <- sapply(X = all.pkgs, FUN = check.install.pkgs)
  
  return(TRUE)
}

find.pkgs <- function(str.in){
  
  require(stringr)
  
  txt.out <- paste(readLines(str.in), collapse = '\n')
  
  out.req.1 <- str_match_all(txt.out, pattern = 'require\\(\"(.*?)\"\\)')[[1]]
  out.req.2 <- str_match_all(txt.out, pattern = 'require\\((.*?)\\)')[[1]]
  
  pkg.out.require <- as.vector(c(out.req.1[,2], out.req.2[,2]))
  
  out1 <- str_match_all(txt.out, pattern = 'library\\(\"(.*?)\"\\)')[[1]]
  out2 <- str_match_all(txt.out, pattern = 'library\\((.*?)\\)')[[1]]
  pkg.out.library <- as.vector(c(out1[,2], out2[,2]))
  
  pkg.out <- c(pkg.out.require, pkg.out.library)
  
  pkg.out <- str_replace_all(pkg.out, pattern = fixed("'"), replacement = '' )

  return(pkg.out)
}

check.install.pkgs <- function(pkg.in){
  cat('\nInstalling', pkg.in)
  
  my.installed.pkgs <- installed.packages()
  
  if ( !(pkg.in %in% my.installed.pkgs[,1]) ){
    cat('- Installing', pkg.in)
    install.packages(pkg.in)
  } else { cat('- Already installed')}
  
}