Variable names

• can contain letters, numbers and some symbols
• can only begin with a letter or a dot followed by a letter
• distinguish between upper and lower case

Examples

• x1, x1.a
• .abc
• this_is_an_informative_variable_name.v1
• another.style.of.a.name
• orEvenThisWay

Data types

• numeric()
• character()
• logical()
• integer()
• complex()
• …

Assign a value to a variable:

• a <- value
• a = value

Operators

• numeric: +, -, *, ^, /, x %% y, …
• logical: | (or), & (and), ! (not), ==, <, <=, >, >=, …
• subset: [, e.g., x[c(2, 3)]
• assignment: [<-, e.g., x[c(1, 3)] <- c(4, 5)
• other: is.na(), as.character(), …
• Quick-R: operators

Operations

5 + 4

## [1] 9

3^2

## [1] 9

x = 5
y = 2
x^2

## [1] 25

x/y

## [1] 2.5

2*x

## [1] 10

sin(x*y)

## [1] -0.5440211

Vectorized operations

x <- 1:3        # sequence of integers from 1 to 3
y <- c(2,4,7)
x; y; x + y     # separate commands by semicolon

## [1] 1 2 3

## [1] 2 4 7

## [1]  3  6 10

x + 4           # recycling

## [1] 5 6 7