Install required packages mentionned in a project

install_packages.r

# list required packages
list_r_files = function() {
  list.files(patt = "(?i)\\.(r|rmd)$", full = TRUE, recursive = TRUE)
}

regular_expression <- function(x, p) regmatches(x, regexec(p, x))

last = function(x) x[length(x)]

scan_packages = function(x) {
  expr = '(library|require)\\("(.+)"\\)'
  m = regular_expression(readLines(x), expr)
  unlist(lapply(m, last))
}

installed_packages = function() unique(unlist(library()$results[, 1]))

# usage
pack = unique(unlist(lapply(list_r_files(), scan_packages)))
print(setdiff(pack, installed_packages()))
install.packages(setdiff(pack, installed_packages()))