Introduction to R

R is a versatile, open source programming/scripting language that's useful both for statistics but also data science. Inspired by the programming language [S][S].

• Open source software under [GPL][].
• Superior (if not just comparable) to commercial alternatives. R has over 5,000 user contributed packages at this time. It's widely used both in academia and industry.
• Available on all platforms.
• Not just for statistics, but also general purpose programming.
• Is object oriented and functional.
• Large and growing community of peers.

How to run R

You can run R interactively or in batch mode.

Interactive mode

e.g. type in R from the shell. The window that appears is called the R console. Any command you type into the prompt is interpreted by the R kernel. An output may or may not be printed to the screen depending on the types of commands that you run.

Batch mode

You can also run one or more R scripts in batch mode.

$ R CMD BATCH script_1.R script_2.R

You can also script inline using Rscript -e.

Example

# Notice how we use a semi-colon to separate multiple commands in a single line
$ Rscript -e "library(knitr); knit('script.Rmd')"

Viewing objects in your global environment and how to clean them up

List objects in your current environment

ls()

remove objects from your current environment

x <- 5
rm(x)
x

## Error: object 'x' not found

remove all objects from your current environment

rm(list = ls())

Notice that we have nested one function inside another.

Use # signs to comment. Comment liberally in your R scripts. Anything to the right of a # is ignored by R.

Assignment operator

<- is the assignment operator. Assigns values on the right to objects on the left. Mostly similar to = but not always. Learn to use <- as it is good programming practice. Using = in place of <- can lead to issues down the line.

Package management

• install.packages("package-name") will download a package from one of the CRAN mirrors assuming that a binary is available for your operating system. If you have not set a preferred CRAN mirror in your options(), then a menu will pop up asking you to choose a location.

• Use old.packages() to list all your locally installed packages that are now out of date. update.packages() - will update all packages in the known libraries interactively. This can take a while if you haven't done it recently. To update everything without any user intervention, use the ask = FALSE argument.

update.packages(ask = FALSE)

Quitting R

type in quit() or q() and answer y to quit.