Re-install missing R packages when you migrate from one R version to another (e.g. from 4.3 to 4.5)

installMissingPackages.R

### Usage example:
# installMissingPackages(4.3, 4.5)


library(magrittr)

getPackages <- function(version) {
  stopifnot(is.numeric(version),
            length(version)==1,
            version==round(version,1))
  .libPaths() %>%
    .[1] %>%
    sub('^(.+)/.+$',paste0('\\1/',version),.) %>% 
    list.dirs(full.names=FALSE,recursive=FALSE)
}

installMissingPackages <- function(version.old, version.new) {
  packages_to_be_installed <-
    getPackages(version.old) %>% 
    setdiff(getPackages(version.new))
  message('\n',length(packages_to_be_installed),' packages to be installed.\n')
  for (p in packages_to_be_installed)
    if (!p %in% row.names(installed.packages())) {
      message('\n====== Installing `',p,'` ======')
      install.packages(p)
    }
}