Installing and loading packages

After successfully installing R, users can download, install, and update packages from the repositories. As R allows users to create their own packages, official and non-official repositories are provided to manage these user-created packages. CRAN is the official R package repository. Currently, the CRAN package repository features 11,589 available packages (as of 10/11/2017). Through the use of the packages provided on CRAN, users may extend the functionality of R to machine learning, statistics, and related purposes. CRAN is a network of FTP and web servers around the world that store identical, up-to-date versions of code and documentation for R. You may select the closest CRAN mirror to your location to download packages.

Getting ready

Start an R session on your host computer.

How to do it...

Perform the following steps to install and load R packages:

Load a list of installed packages:

        > library()

Set the default CRAN mirror:

        > chooseCRANmirror()

R will return a list of CRAN mirrors, and then ask the user to either type a mirror ID to select it, or enter zero to exit:

Install a package from CRAN; take package e1071 as an example:

        > install.packages("e1071")

Update a package from CRAN; take package e1071 as an example:

        > update.packages("e1071")

Load the package:

        > library(e1071)

If you would like to view the documentation of the package, you can use the help function:

        > help(package ="e1071")

If you would like to view the documentation of the function, you can use the help function:

        > help(svm, e1071)

Alternatively, you can use the help shortcut, ?, to view the help document for this function:

        > ?e1071::svm

If the function does not provide any documentation, you may want to search the supplied documentation for a given keyword. For example, if you wish to search for documentation related to svm:

        > help.search("svm")

Alternatively, you can use ?? as the shortcut for help.search:

        > ??svm

To view the argument taken for the function, simply use the args function. For example, if you would like to know the argument taken for the lm function:

        > args(lm)

Some packages will provide examples and demos; you can use example or demo to view an example or demo. For example, one can view an example of the lm package and a demo of the graphics package by typing the following commands:

        > example(lm)
        > demo(graphics)

To view all the available demos, you may use the demo function to list all of them:

        > demo()

How it works...

This recipe first introduces how to view loaded packages, install packages from CRAN, and load new packages. Before installing packages, those of you who are interested in the listing of the CRAN package can refer to http://cran.r-project.org/web/packages/available_packages_by_name.html.

When a package is installed, documentation related to the package is also provided. You are, therefore, able to view the documentation or the related help pages of installed packages and functions. Additionally, demos and examples are provided by packages that can help users understand the capability of the installed package.