Introduction

What Is R?

R is an open-source language used by statisticians, data scientists, and researchers to analyse data, run statistical tests, and create charts. Unlike general-purpose languages, R was built from the ground up around one idea: working with data should be simple and natural.

You can install R for free from cran.r-project.org, and most people also install RStudio — a free, friendly editor that makes writing and running R code much easier (console, script editor, plot viewer, and file browser all in one window).

Your First Line of R Code

Open R or RStudio and type the following into the console, then press Enter.

print("Hello, World!")

[1] "Hello, World!"

The [1] in front of the output just means "this is the first element of the result" — you will see this a lot in R, because almost everything in R is technically a vector (a sequence of values), even a single line of text.

Variables and Assignment

A variable stores a value so you can reuse it later. In R, the idiomatic way to assign a value to a variable is the arrow <- (you can also use =, but <- is what most R code and documentation use).

name <- "Rafi"
age  <- 23
is_student <- TRUE

print(name)
print(age)
print(is_student)

[1] "Rafi"
[1] 23
[1] TRUE

Basic Data Types

Every value in R belongs to one of a handful of basic types. Knowing these is the foundation for everything else in this guide.

• numeric — any number with or without decimals, e.g. 10, 3.14
• integer — whole numbers, written with an L suffix, e.g. 5L
• character — text, always in quotes, e.g. "hello"
• logical — TRUE or FALSE
• complex — numbers with an imaginary part, e.g. 2+3i (rarely used by beginners)

Use class() to check the type of any value or variable:

class(10)
class(5L)
class("hello")
class(TRUE)

[1] "numeric"
[1] "integer"
[1] "character"
[1] "logical"

Comments

Anything after a # on a line is a comment — R ignores it completely. Comments explain your code to your future self (and to anyone else reading it).

# this calculates the area of a circle
radius <- 5
area <- pi * radius^2   # pi is a built-in constant
area

[1] 78.53982

Getting Help

R has excellent built-in documentation. If you ever forget how a function works, don't guess — ask R directly.

?mean        # opens the help page for mean()
help("sum") # same thing, alternate syntax
args(round) # shows just the arguments a function accepts