Section 5 Packages

R has a large number of packages available (over 16,000 at the time of writing). R packages typically contain extra functions based around some theme (e.g. a collection of functions to enable you to fit a particular type of statistical model.)

Some packages come pre-installed with R, and others need to be installed manually.

5.1 Installing a package

Use the command install.packages() to install a package. If the package you want requires other packages, R will install them too, so installation can take a while! During the installation process, you may get a message along the lines of

...There are binary versions available but the source versions are later. Do you want to install from sources the package which needs compilation?

Answering n (for no) is usually safe, in case your computer isn’t set up for installing packages ‘from source’.

As an example, we’ll install the zoo package, which has some helpful functions for working with time series data.

install.packages("zoo")

Only type an install.packages() command in the console window. Do not use this command in a script or R Markdown document (we will study scripts and R Markdown shortly). This will avoid you repeatedly installing the same package.

5.2 Updating packages

It’s worth occasionally checking for package updates. In particular, if a package you’re using doesn’t appear to be working properly, look to see if there’s an update. In RStudio, click on the Packages tab, and then click on Update to see what’s available.

5.3 Using packages

A package only needs to be installed once, but you need to load the package every time you start R, or use the :: syntax. For example, the zoo package has a function rollmean() for computing rolling means (e.g. mean at time \(t\) of the most recent 4 observations up to time \(t\)). As an example, suppose we have a vector x:

x <- 10:20

We can either use the syntax package-name::function.

zoo::rollmean(x, k = 4)

## [1] 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5

or we can first do

library(zoo)

## 
## Attaching package: 'zoo'

## The following objects are masked from 'package:base':
## 
##     as.Date, as.Date.numeric

and then any function within the package can be used directly:

rollmean(x, k = 4)

## [1] 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5

For some packages (e.g. ggplot2), it will be obvious from the commands what package is being used. Otherwise, I recommend you use the :: syntax as it will make your code easier to read; it can be helpful to be explicit about which package a function has come from.

5.4 Is there a package for…?

You shouldn’t need to search for packages in this module, but you might wish to find a package to do something on another module.

If you’re searching for a package to do something, one simple approach is to include “R CRAN” in your web search, e.g. you might search for R CRAN lasso if you were looking for a package to implement a statistical technique called the “lasso”. (CRAN is the main repository for R packages).

You could also try browsing the CRAN Task Views. These discuss some of the packages that are available for particular topics (e.g Bayesian inference, machine learning, time series analysis etc.)