Variables and Assignment

A variable gives a name to a value so you can use it later.

Real-world analogy: a variable is a labeled box. You write a name on the box and put something inside; later you refer to the box by its name.

Syntax

R's assignment operator is <- (a "less than" sign and a hyphen):

city <- "Lagos"
temperature <- 24

= also works for assignment, but <- is the standard R style, and = is normally reserved for naming function arguments. RStudio types <- for you with Alt + - (Option + - on macOS).

Example

city <- "Lagos"
temperature <- 24
city
temperature

temperature <- 27
temperature

temperature <- temperature + 1
temperature

Expected output

[1] "Lagos"
[1] 24
[1] 27
[1] 28

Assigning a new value replaces the old one. R has no += operator — write temperature <- temperature + 1.

Naming

• Use descriptive names in snake_case: mean_height, total_sales.
• Avoid names of common functions like mean, c, t, or data — R allows it, but it's confusing.

Listing and removing variables

rm(list = ls())
x <- 1
y <- 2
ls()
rm(x)
ls()

[1] "x" "y"
[1] "y"

Common mistakes

• Using a variable before creating it: Error: object 'total' not found.
• Writing x < - 5 (with a space) — that compares x with -5 instead of assigning.

Practice

Create a variable apples equal to 5, add 3 to it, and print I have 8 apples using cat.

apples <- 5
apples <- apples + 3
cat("I have", apples, "apples\n")

I have 8 apples