R list

A list in R is a collection of objects that can store different types of data, such as numbers, strings, vectors, another list, and even matrices and functions.

To create a list in R, use the list() function.

Here is an example where we create a list containing strings, vectors, and numbers:

Example

list_data <- list("tutorialpro", "google", c(11,22,33), 123, 51.23, 119.1)
print(list_data)

Executing the above code produces the following output:

[[1]]
[1] "tutorialpro"

[[2]]
[1] "google"

[[3]]
[1] 11 22 33

[[4]]
[1] 123

[[5]]
[1] 51.23

[[6]]
[1] 119.1

We can use the names() function to name the elements of the list:

Example

# List containing vector, matrix, list
list_data <- list(c("Google","tutorialpro","Taobao"), matrix(c(1,2,3,4,5,6), nrow = 2),
   list("tutorialpro",12.3))

# Set names for list elements
names(list_data) <- c("Sites", "Numbers", "Lists")

# Display the list
print(list_data)

Executing the above code produces the following output:

$Sites
[1] "Google" "tutorialpro" "Taobao"

$Numbers
     [,1] [,2] [,3]
[1,]    1    3    5
[2,]    2    4    6

$Lists
$Lists[[1]]
[1] "tutorialpro"

$Lists[[2]]
[1] 12.3

Accessing List Elements

Elements in a list can be accessed using their index. If the elements are named using the names() function, we can also access them by their names:

Example

# List containing vector, matrix, list
list_data <- list(c("Google","tutorialpro","Taobao"), matrix(c(1,2,3,4,5,6), nrow = 2),
   list("tutorialpro",12.3))

# Set names for list elements
names(list_data) <- c("Sites", "Numbers", "Lists")

# Display the first element of the list
print(list_data[1])

# Access the third element of the list
print(list_data[3])

# Access the first vector element
print(list_data$Numbers)

Executing the above code produces the following output:

$Sites
[1] "Google" "tutorialpro" "Taobao"

$Lists
$Lists[[1]]
[1] "tutorialpro"

$Lists[[2]]
[1] 12.3

     [,1] [,2] [,3]
[1,]    1    3    5
[2,]    2    4    6

Manipulating List Elements

We can add, delete, and update elements in a list as shown in the following example:

Example

# List containing vector, matrix, list
list_data <- list(c("Google","tutorialpro","Taobao"), matrix(c(1,2,3,4,5,6), nrow = 2),
   list("tutorialpro",12.3))

# Set names for list elements
names(list_data) <- c("Sites", "Numbers", "Lists")

# Add an element
list_data[4] <- "New Element"
print(list_data[4])

# Delete an element
list_data[4] <- NULL

# Output after deletion is NULL
print(list_data[4])

# Update an element
list_data[3] <- "I replaced the third element"
print(list_data[3])

Executing the above code produces the following output:

[[1]]
[1] "New Element"

$<NA>
NULL

$Lists
[1] "I replaced the third element"

Merging Lists

We can merge multiple lists into one using the c() function:

Example

# Create two lists
list1 <- list(1,2,3)
list2 <- list("Google","tutorialpro","Taobao")

# Merge lists
merged.list <- c(list1,list2)

# Display the merged list
print(merged.list)

Executing the above code produces the following output:

[[1]]
[1] 1

[[2]]
[1] 2

[[3]]
[1] 3

[[4]]
[1] "Google"

[[5]]
[1] "tutorialpro"

[[6]]
[1] "Taobao"

[1] "tutorialpro"

[[6]] [1] "Taobao"

Convert List to Vector

To convert a list to a vector, you can use the unlist() function. Converting a list to a vector can facilitate arithmetic operations:

Example

# Create a list
list1 <- list(1:5)
print(list1)

list2 <- list(10:14)
print(list2)

# Convert to vector
v1 <- unlist(list1)
v2 <- unlist(list2)

print(v1)
print(v2)

# Add two vectors
result <- v1 + v2
print(result)

Executing the above code will produce the following output:

[[1]]
[1] 1 2 3 4 5

[[1]]
[1] 10 11 12 13 14

[1] 1 2 3 4 5
[1] 10 11 12 13 14
[1] 11 13 15 17 19