Elegant way to check for missing packages and inst

Question

I seem to be sharing a lot of code with coauthors these days. Many of them are novice/intermediate R users and don't realize that they have to install packages they don't already have.

Is there an elegant way to call installed.packages(), compare that to the ones I am loading and install if missing?

Answer 1

Dason K. and I have the pacman package that can do this nicely. The function p_load in the package does this. The first line is just to ensure that pacman is installed.

if (!require("pacman")) install.packages("pacman")
pacman::p_load(package1, package2, package_n)

Answer 2

Regarding your main objective " to install libraries they don't already have. " and regardless of using " instllaed.packages() ". The following function mask the original function of require. It tries to load and check the named package "x" , if it's not installed, install it directly including dependencies; and lastly load it normaly. you rename the function name from 'require' to 'library' to maintain integrity . The only limitation is packages names should be quoted.

require <- function(x) { 
  if (!base::require(x, character.only = TRUE)) {
  install.packages(x, dep = TRUE) ; 
  base::require(x, character.only = TRUE)
  } 
}

So you can load and installed package the old fashion way of R. require ("ggplot2") require ("Rcpp")

Answer 3

Using lapply family and anonymous function approach you may:

1. Try to attach all listed packages.
2. Install missing only (using || lazy evaluation).
3. Attempt to attach again those were missing in step 1 and installed in step 2.

4. Print each package final load status (TRUE / FALSE).

   req <- substitute(require(x, character.only = TRUE))
   lbs <- c("plyr", "psych", "tm")
   sapply(lbs, function(x) eval(req) || {install.packages(x); eval(req)})
   
   plyr psych    tm 
   TRUE  TRUE  TRUE