Check and load R packages

checkpkgs.R

# different (similar) ways to check and load pkgs in R
# method 1
check_pkgs <- function(pkg_list){
      for(pkg in pkg_list) {
        if(!require(pkg, character.only = T)){
          stop('Please install the ', pkg, ' package, using "install.packages(', pkg, ')"', call. = F)
        }
      }
    }
check_pkgs(pkg_list = c("asserththat", "ggplot2"))

# method 1 + install missing packages
check_pkgs <- function(pkg_list){
      for(pkg in pkg_list) {
        if(!require(pkg, character.only = T)){
            cat('Installing the ', pkg, ' package, using "install.packages(', pkg, ')')
            install.packages(pkg, repos = "http://cran.us.r-project.org")
        }
      }
    }
check_pkgs(pkg_list = c("asserththat", "ggplot2"))




# method 2
check_pkgs <- function(...){
      for (pkg in c(...)) {
        if(!require(pkg, character.only = T)){
          stop('Please install the ', pkg, ' package, using "install.packages(', pkg, ')"', call. = F)
        }
      }
    }
check_pkgs("assertthat", "ggplot2")

# method 3
check_pkgs <- function(...){
      for (pkg in c(...)) {
        if(pkg %in% rownames(installed.packages())) {
          cat("- Loading required package: ", pkg, "\n")
          do.call('library', list(pkg))
        } else {
          stop('Please install the ', pkg, ' package, using "install.packages(', pkg, ')"', call. = F)
        }
      }
    }
check_pkgs("assertthat", "ggplot2")