Named List in R Programming

A list is an object in R Language which consists of heterogeneous elements. A list can even contain matrices, data frames, or functions as its elements. The list can be created using list() function in R. Named list is also created with the same function by specifying the names of the elements to access them. Named list can also be created using names() function to specify the names of elements after defining the list. In this article, we'll learn to create named list in R using two different methods and different operations that can be performed on named lists.

Syntax: names(x) <- value Parameters: x: represents an R object value: represents names that has to be given to elements of x object

Creating a Named List

# Defining a list with names
x <- list(mt = matrix(1:6, nrow = 2),
          lt = letters[1:8],
          n = c(1:10))

# Print whole list
cat("Whole List:\n")
print(x)

Whole List:
$mt
     [,1] [,2] [,3]
[1,]    1    3    5
[2,]    2    4    6

$lt
[1] "a" "b" "c" "d" "e" "f" "g" "h"

$n
 [1]  1  2  3  4  5  6  7  8  9 10

# Defining list
x <- list(matrix(1:6, nrow = 2),
          letters[1:8],
          c(1:10))

# Print whole list
cat("Whole list:\n")
print(x)

Whole list:
[[1]]
     [,1] [,2] [,3]
[1,]    1    3    5
[2,]    2    4    6

[[2]]
[1] "a" "b" "c" "d" "e" "f" "g" "h"

[[3]]
 [1]  1  2  3  4  5  6  7  8  9 10

Accessing components of Named List

# Defining a list with names
x <- list(mt = matrix(1:6, nrow = 2),
          lt = letters[1:8],
          n = c(1:10))

# Print list elements using the names given
# Prints element of the list named "mt"
cat("Element named 'mt':\n")
print(x$mt)
cat("\n")

# Print element of the list named "n"
cat("Element named 'n':\n")
print(x$n)

Element named 'mt':
     [,1] [,2] [,3]
[1,]    1    3    5
[2,]    2    4    6

Element named 'n':
 [1]  1  2  3  4  5  6  7  8  9 10

Modifying components of Named List

# Defining a named list
lt <- list(a = 1,
           let = letters[1:8],
           mt = matrix(1:6, nrow = 2))

cat("List before modifying:\n")
print(lt)

# Modifying element named 'a'
lt$a <- 5

cat("List after modifying:\n")
print(lt)

List before modifying:
$a
[1] 1

$let
[1] "a" "b" "c" "d" "e" "f" "g" "h"

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

List after modifying:
$a
[1] 5

$let
[1] "a" "b" "c" "d" "e" "f" "g" "h"

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

Deleting components from Named List

# Defining a named list
lt <- list(a = 1,
           let = letters[1:8],
           mt = matrix(1:6, nrow = 2))

cat("List before deleting:\n")
print(lt)

# Modifying element named 'a'
lt <- within(lt, rm(a))

cat("List after deleting:\n")
print(lt)

List before deleting:
$a
[1] 1

$let
[1] "a" "b" "c" "d" "e" "f" "g" "h"

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

List after deleting:
$let
[1] "a" "b" "c" "d" "e" "f" "g" "h"

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