R Lists

Lists are a collection of objects in R language, which can be used to save different types of data, such as numbers, strings, vectors, another list, etc., of course, it can also contain matrices and functions.

R language creates lists using the list() function.

As shown in the following example, we create a list that contains strings, vectors, and numbers:

list_data <-　list("w3codebox",　"google",　c(11,22,33),　123,　51.23,　119.1)
print(list_data)

The output of the above code is:

[[1]]
[1] "w3codebox"
[[2]]
[1]　"google"
[[3]]
[1]　11　22　33
[[4]]
[1]　123
[[5]]
[1]　51.23

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

# List contains vectors, matrices, and lists
list_data <-　list(c("Google","w3codebox","Taobao"), matrix(c(1,2,3,4,5,6), nrow =　2),
　　　list("w3codebox",12.3))
# Set names for list elements
names(list_data) <-　c("Sites", "Numbers", "Lists")
# Display the list
print(list_data)

The output of the above code is:

$Sites
[1]　"Google"　"w3codebox"　"Taobao"
$Numbers
　　　　　[,1]　[,2]　[,3]
[1,]　　　　1　　　　3　　　　5
[2,]　　　　2　　　　4　　　　6
$Lists
$Lists[[1]]
[1] "w3codebox"
$Lists[[2]]
[1]　12.3

Access the list

List elements can be accessed using indices, if using to names() After naming the function, we can also access it using the corresponding name:

# List contains vectors, matrices, and lists
list_data <-　list(c("Google","w3codebox","Taobao"), matrix(c(1,2,3,4,5,6), nrow =　2),
　　　list("w3codebox",12.3))
# Set names for list elements
names(list_data) <-　c("Sites", "Numbers", "Lists")
# Display the list
print(list_data[1])
# Access the third element of the list
print(list_data[3])
# Access the first element of the vector
print(list_data$Numbers)

The output of the above code is:

$Sites
[1]　"Google"　"w3codebox"　"Taobao"
$Lists
$Lists[[1]]
[1] "w3codebox"
$Lists[[2]]
[1]　12.3
　　　　　[,1]　[,2]　[,3]
[1,]　　　　1　　　　3　　　　5
[2,]　　　　2　　　　4　　　　6

Operate list elements

We can perform operations such as adding, deleting, and updating lists, as shown in the following examples:

# List contains vectors, matrices, and lists
list_data <-　list(c("Google","w3codebox","Taobao"), matrix(c(1,2,3,4,5,6), nrow =　2),
　　　list("w3codebox",12.3))
# Set names for list elements
names(list_data) <-　c("Sites", "Numbers", "Lists")
# Add element
list_data[4] <-　"New element"
print(list_data[4])
# Delete element
list_data[4] <-　NULL
# Delete and output as NULL
print(list_data[4])
# Update element
list_data[3] <-　"I replace the third element"
print(list_data[3])

The output of the above code is:

[[1]]
[1] "New element"
$<NA>
NULL
$Lists
[1] "I replace the third element"

Merge Lists

We can use the c() function to merge multiple lists into one list:

# Create two lists
list1　<-　list(1,2,3)
list2　<-　list("Google","w3codebox","Taobao")
# Merge lists
merged.list <-　c(list(1,list2)
# Display the merged list
print(merged.list)

The output of the above code is:

[[1]]
[1]　1
[[2]]
[1]　2
[[3]]
[1]　3
[[4]]
[1] "Google"
[[5]]
[1] "w3codebox"
[[6]]
[1] "Taobao"

List to Vector

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

# 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)
# Two vector addition
result <-　v1+v2
print(result)

The output of the above code is:

[[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