Lists are objects in R that contain elements of different types, such as numbers, strings, vectors, and other lists within them. A list can contain a matrix or a function as its elements.
Objects in R, Lists are created using the List () function.
Create a list
The following is an example of how to create a list of logical strings, numbers, and values.
# Create a list containing strings, numbers, vectors and a logical
# values.
list_data <- list (“Red”, “Green”, c (21,32,11), TRUE, 51.23, 119.1)
print (list_data)
When we run the above code; The following results are generated:
[[1]]
[1] “Red”
[[2]]
[1] “Green”
[[3]]
[1] 21 32 11
[[4]]
[1] TRUE
[[5]]
[1] 51.23
[[6]]
[1] 119.1
Name the members of the list
List members can be named and accessed using their names.
# Create a list containing a vector, a matrix and a list.
list_data <- list (c (“Jan”, “Feb”, “Mar”), matrix (c (3,9,5,1, -2,8), nrow = 2),
list (“green”, 12.3))
# Give names to the elements in the list.
names (list_data) <- c (“1st Quarter”, “A_Matrix”, “A Inner list”)
# Show the list.
print (list_data)
When we run the above code; The following result is created:
$ `1st_Quarter`
[1] “Jan” “Feb” “Mar”
$ A_Matrix
[, 1] [, 2] [, 3]
[1,] 3 5 -2
[2,] 9 1 8
$ A_Inner_list
$ A_Inner_list [[1]]
[1] “green”
$ A_Inner_list [[2]]
[1] 12.3
Access the elements of a list
They can be accessed using the index of members of a list. In the case of named lists; They can be accessed using the names of Nir members.
We use the list in the example above; We continue:
# Create a list containing a vector, a matrix and a list.
list_data <- list (c (“Jan”, “Feb”, “Mar”), matrix (c (3,9,5,1, -2,8), nrow = 2),
list (“green”, 12.3))
# Give names to the elements in the list.
names (list_data) <- c (“1st Quarter”, “A_Matrix”, “A Inner list”)
# Access the first element of the list.
print (list_data [1])
# Access the thrid element. As it is also a list, all its elements will be printed.
print (list_data [3])
# Access the list element using the name of the element.
print (list_data $ A_Matrix)
When we run the above code; The following result is obtained:
$ `1st_Quarter`
[1] “Jan” “Feb” “Mar”
$ A_Inner_list
$ A_Inner_list [[1]]
[1] “green”
$ A_Inner_list [[2]]
[1] 12.3
[, 1] [, 2] [, 3]
[1,] 3 5 -2
[2,] 9 1 8
Hire members of a list
We can list the elements as shown below; Add or remove. We can only add elements to the bottom of the list; Also, we can only delete the elements at the bottom of a list. But we can update any element.
# Create a list containing a vector, a matrix and a list.
list_data <- list (c (“Jan”, “Feb”, “Mar”), matrix (c (3,9,5,1, -2,8), nrow = 2),
list (“green”, 12.3))
# Give names to the elements in the list.
names (list_data) <- c (“1st Quarter”, “A_Matrix”, “A Inner list”)
# Add element at the end of the list.
list_data [4] <- “New element”
print (list_data [4])
# Remove the last element.
list_data [4] <- NULL
# Print the 4th Element.
print (list_data [4])
# Update the 3rd Element.
list_data [3] <- “updated element”
print (list_data [3])
When we execute the above code; The following result is obtained:
[[1]]
[1] “New element”
$ <NA>
NULL
$ `A Inner list`
[1] “updated element”
Merge lists
You can merge multiple lists into one list. This is done by placing all the lists in a list () function.
# Create two lists.
list1 <- list (1,2,3)
list2 <- list (“Sun”, “Mon”, “Tue”)
# Merge the two lists.
merged.list <- c (list1, list2)
# Print the merged list.
print (merged.list)
When we run the above code; The following result is obtained:
[[1]]
[1] 1
[[2]]
[1] ۲
[[3]]
[1] 3
[[4]]
[1] “Sun”
[[5]]
[1] “Mon”
[[6]]
[1] “Tue”
Convert list to vector
A list can be turned into a vector; In such a way that the elements of that vector can be used for future use. All arithmetic operations on vectors can be performed after the list has been converted to vectors; Applied. To perform this conversion, we use the unlist () function . This function takes the list as input and generates a vector.
# Create lists.
list1 <- list (1: 5)
print (list1)
list2 <-list (10:14)
print (list2)
# Convert the lists to vectors.
v1 <- unlist (list1)
v2 <- unlist (list2)
print (v1)
print (v2)
# Now add the vectors
result <- v1 + v2
print (result)
When we run the above code; The following result is obtained:
[[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