Variables

A variable is used to store data that can be accessed later by subsequent code. In R, there are no variable “declaration” commands. Instead, they are created with the assignment operator, <- (The more familiar assignment operator, =, can be used instead, but is discouraged).

# This creates a variable containing the string "value"
variable <- "value"

The assignment operator can be chained together to initialize multiple variables at once:

var1 <- var2 <- var3 <- 0

In R, writing a defined variable name by itself on a line has the effect of printing its associated value:

score <- 100

# This line:
score # Output 100

# Has the same effect as this line:
print(score) # Output 100

Variable Names

R variables must adhere to the following naming conventions:

• The name can be a combination of letters, digits, period(.) and underscore(_).
• It must start with a letter or a period.
• If it starts with a period, the second character cannot be a number.
• It cannot start with a number or an underscore.
• Variable names are case-sensitive.
• Reserved words (TRUE, FALSE, print, etc.) cannot be used as variable names.

Examples

The following code snippet shows examples of valid variable names in R:

foo <- 1
Foo <- 2 # A different variable from "foo" above
.bar <- TRUE
foo_bar <- "value"
3.5 -> Foo123.4 # Rightward assignment.