R append() Function: Complete Guide

The append() function in R concatenates values to a vector or list at a specified position. It returns a new object without modifying the original.

You can add a single or multiple elements to a vector or list.

Syntax

append(obj, values, after = length(x))

Parameters

Appending a single element to a Vector

By default, the append() function will append an element at the end of the vector if you don’t specify the position.

data <- 1:3

element <- 19

cat(data, "\n")

modified_vec <- append(data, element)

cat("After appending an element to a vector", "\n")

cat(modified_vec)

Output

1 2 3
After appending an element to a vector
1 2 3 19 

Appending multiple elements to a Vector

When you append multiple elements to a vector, you can append them as a separate vector rather than as individual elements. What I mean by this is that If you have multiple elements, then create a vector of it and then append it to an existing vector. That way, you have an output vector that contains multiple appended elements.

v1 <- 1:3
v2 <- 19:21

cat("Before appending elements to v1", "\n")

cat(v1, "\n")

modified_data <- append(v1, v2)

cat("After appending multiple elements to a v1", "\n")

cat(modified_data)

Output

Before appending elements to v1
1 2 3 

After appending multiple elements to a v1
1 2 3 19 20 21

Adding to the specific position

The function provides an “after” argument that you can use to pinpoint a specific position and append to it.

v1 <- 1:4
v2 <- 19

cat("Before adding element to v1", "\n")

cat(v1, "\n")

cat("Appending element after index 2", "\n")

modified_data <- append(v1, v2, 2)

cat(modified_data)

Output

Before adding element to v1
1 2 3 4
Appending element after index 2
1 2 19 3 4

Appending a single element to a List

As we discussed earlier, the append() function can also be used to add elements to a list. Its usage is not limited to a vector.

main_list <- list(a = 1, b = 2)

element <- list(c = 3)

append(main_list, element) # Adds 'c=3' to the end

Output

$a
[1] 1

$b
[1] 2

$c
[1] 3

Appending multiple elements to a List

When you append multiple elements to a list, you can append them as a separate list rather than as individual elements.

main_list <- list(a = 1, b = 2)

append_list <- list(c = 3, d = 4, e = 5)

append(main_list, append_list)

Output

$a
[1] 1

$b
[1] 2

$c
[1] 3

$d
[1] 4

$e
[1] 5

Appending elements to a specific position

Same as a vector, you can specify the “after” argument to define the exact position of insertion. It will append after that index that you defined.

main_list <- list(a = 1, b = 2, c=3)

append_list <- list(d = 4)

append(main_list, append_list, after = 1) # Inserts after the first element

Output

$a
[1] 1

$d
[1] 4

$b
[1] 2

$c
[1] 3

You can see that we appended after index 1, which is position number 2. List index starts with 1.