# Lesson 3. Install & Use Packages in R

## Install a Package

In this tutorial, we will walk you through installing the rmarkdown, knitr and ggplot2 packages for R.

## Learning Objectives

At the end of this activity, you will:

• Know how to install an R package using R Studio.
• Be able to explain what a package is in R.

## What is a Package?

A package, in R is a bundle of pre-built functionality. Think of it like a toolbox. Except for the tools may do things like calculate a mathematical function e.g. sum or create a plot.

## Install a Package

In R we install packages using the install.packages("packageNameHere") function. Let’s get R Markdown and knitr installed so we can use them in our exercises. In the R console within R Studio, use the code below to install packages individually.

# install knitr
install.packages("knitr")

# install the rmarkdown package
install.packages("rmarkdown")

# install ggplot for plotting
install.packages("ggplot2")

# install dplyr for data manipulation
install.packages("dplyr")


Data tip You can install as many packages as you want in one string of code as follows install.packages(c("name-one", "name-two"))

## Call Package in R

Once the package is installed, to use it, you call the package at the top of your script like this:

# load libraries
library(knitr)
library(rmarkdown)
library(ggplot2)


Note that you don’t need to use quotes around the package name when you call it using the library() function. But you do need the quotes when you install a package.

In our case, the knitr and R Markdown packages load buttons and options within the R Studio environment that we can use. Thus we won’t have to call these two packages in our code in this lesson. However, when we use ggplot2 to plot, we will have to call it. We will see how calling a package works in a later set of lessons.

When you load a library in R, you are telling R to make all of the FUNCTIONS available in the package (think of functions like tools that perform tasks - for example plot()) available to you in your code.

### Where Do R Packages Live?

R packages are most often found on the CRAN repository. When you call install.packages("package-name-here") you are actually downloading the packages from CRAN. However there are other places where you may install packages from including:

• Bioconductor
• github
• and more

Data tip While some R packages are just fine to use. Keep in mind that not all R packages are secure. Learn more.

### Advanced - Install Multiple Packages at Once

You can also install multiple R packages at the same time. To do that, you send the install.packages() function a vector or list of package names.

A vector is a list of objects. the syntax for a vector is:

c("object1", "object2")

you can also store numbers in a vector.

c(1, 5, 74)

So if we want to install rmarkdown, ggplot2 and dplyr all at once, we do this:

# install several packages at once
install.packages(c("rmarkdown", "ggplot2", "dplyr"))