What is a package in R, and how do you install and load packages?

An R package is a collection of functions, code, data, and documentation, representing an extension of the R programming language and designed for solving specific kinds of tasks. R comes with a bunch of preinstalled packages, and other packages can be installed by users from repositories. The most popular centralized repository storing thousands of various R packages is called Comprehensive R Archive Network (CRAN).

To install an R package directly from CRAN, we need to pass the package name enclosed in quotation marks to the install.packages() function, as follows: install.packages("package_name"). To install more than one package from CRAN in one go, we need to use a character vector containing the package names enclosed in quotation marks, as follows: install.packages(c("package_name_1", "package_name_2"). To install an R package manually, we need first to download the package as a zip file on our computer and then run the install.packages() function:

install.packages("path_to_the_locally_stored_zipped_package_file", repos=NULL, type="source")Powered By 

To load an installed R package in the working R environment, we can use either library() or require() functions. Each of them takes in the package name without quotation marks and loads the package, e.g., library(caret). However, the behavior of these functions is different when they can’t find the necessary package: library() throws an error and stops the program execution, while require() outputs a warning and continues the program execution.