install_packages

packages = c('<package1>', '<package2>')

for (package in packages) {
    if (!require(package, character.only=T, quietly=T)) {
        install.packages(package)
        library(package, character.only=T)
    }
}

# Ref: https://stackoverflow.com/questions/5595512/what-is-the-difference-between-require-and-library?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa