Vectors

Vectors are used to store multiple values of the same data type for later use. Unlike other programming languages, vectors in R are not zero-indexed; they start from 1.

Vector Types

Atomic vectors are made with the ‘c()’ function to combine different elements of the same type together:

atomic_vector <- c(element_1, element_2, ... element_N)

Recursive vectors can have elements of any data type and is created with the list() function:

recursive_vector <- list(element_1, element_2, ... element_N)

Examples

The following atomic vectors are created with the c() function:

# Character vector
names <- c('Adam', 'John', 'Walter')
# Integer vector
marks <- c(90, 87, 100, 79, 91)
# Logical vector
booleans <- c(TRUE, FALSE, TRUE)

Apart from the ‘c()’ function, the colon operator (:) can be used to create a vector containing a range of numbers:

# This vector contains all the numbers between 1 and 10
numbers <- 1:10
numbers
# Output: [1] 1 2 3 4 5 6 7 8 9 10

In R, character vectors can contain alphanumeric values and special characters.

alphanumerics <- c('water', 'fire', 'ice', 90)
alphanumerics
# Output: [1] "water" "fire" "ice" "90"

Accessing Vector Elements

The most common way to access vector elements is by index using the subscript operator []:

numbers <- c(65, 49, 55, 36, 126)
numbers[2]
numbers[4]

The output would look like this:

[1] 49
[1] 36

Vector elements can also be accessed by logical indexing:

# Accessing vector elements using logical indexing.
numbers <- c(1, 2, 3, 4, 5)
numbers[numbers < 4]

This would produce the following output:

[1] 1 2 3

Updating a Vector

Vector elements can be updated by specifying the index with the subscript operator ([]) and replacing with the new value:

numbers <- c(2, 5, 1, 7, 9)
cat("Original vector: ", numbers, "\n")
numbers[3] = 8
cat("Third element changed: ", numbers, "\n")
numbers[1] = 0
cat("First element changed: ", numbers)

To start, the third element in numbers is updated to 8. Next, the first element is updated to 0. This will produce the following output:

Original vector: 2 5 1 7 9
Third element changed: 2 5 8 7 9
First element changed: 0 5 8 7 9

Vector Recycling

Vector recycling is a process in which two vectors of different lengths are operated upon such that the elements of the shorter vector are repeated to match the length of the longer vector.

Example

The following example presents two cases of vector recycling using addition, which requires the two vectors to be equal in length.

Case 1 is when the two vector lengths are equal:

numbers_1 <- c(1, 2, 3, 4, 5)
numbers_2 <- c(3, 4, 5, 6, 7)
sum <- numbers_1 + numbers_2
sum
# Output: [1] 4 6 8 10 12

Case 2 is when the vector lengths are unequal:

numbers_1 <- c(1, 2, 3, 4, 5, 6)
numbers_2 <- c(3, 4)
sum <- numbers_1 + numbers_2
sum
# Output: [1] 4 6 6 8 8 10

Here, the first two elements of numbers_1 are added to the first, and only, two elements of numbers_2. Then, to complete the addition operation, R repeats (or recycles) the elements of the smaller numbers_2 vector (3 and 4) until the end of numbers_1 is reached.