Modifying

Now let's move on to list modification tools. First, let's consider methods of adding an element (or elements) to a list.

The first method is convenient for adding single values. You need to assign a new value to the new index or naming. For example, let's add a new element named integer with the value of 23L.

# Creating a list

test <- list(text = "Text", number = 42, logical = TRUE)

# Add new value

test['integer'] <- 23L

test # Output modified list


              12345
            
# Creating a list
test <- list(text = "Text", number = 42, logical = TRUE)
# Add new value
test['integer'] <- 23L
test # Output modified list

Note

Unlike in the list() function, you must use quotes for naming while adding a new element. You can also 'merge' two lists by placing them inside a vector. This approach will 'connect' two lists together.

# Two lists

list1 <- list("first", 10)

list2 <- list("second", 20)

# Merge two lists

list12 <- c(list1, list2)

list12 # Output its value


              123456
            
# Two lists
list1 <- list("first", 10)
list2 <- list("second", 20)
# Merge two lists
list12 <- c(list1, list2)
list12 # Output its value

Also, you can delete elements from the list. To do it, assign to the necessary index value NULL. For example, let's remove TRUE from the first example.

test <- list(text = "Text", number = 42, logical = TRUE)

test['integer'] <- 23L

# Remove the third element

test$logical <- NULL

# Output modified list

test


              123456
            
test <- list(text = "Text", number = 42, logical = TRUE)
test['integer'] <- 23L
# Remove the third element
test$logical <- NULL
# Output modified list
test

As you can see, you removed the TRUE element. Finally, to change the existing value of the list, reassign the new value to the existing index/naming. For example, if you write test[1] <- "word", then instead of "Text", the first element will be "word".

Opgave

Swipe to start coding

Given list info from the previous chapter. Your tasks are:

Rewrite the fourth element to 44 (this chapter is the 44th).
Remove the third element (which is 1).
Add a new element named Level with the value of 'Beginner'.
Output modified list info.

Løsning

# Initial list

info <- list("R Introduction", 6, 1, 41)

names(info) <- c('Course name', 'Section', 'Chapter', 'Chapter overall')

# Change the value of the fourth element

info[4] <- 44

# Remove the third element

info[3] <- NULL

# Add new element

info["Level"] <- "Beginner"

# Output modified list

info

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Tak for dine kommentarer!

Sektion 3. Kapitel 4

# Initial list

info <- list("R Introduction", 6, 1, 41)

names(info) <- c('Course name', 'Section', 'Chapter', 'Chapter overall')

# Change the value of the fourth element

___[___] <- ___

# Remove the third element

___[___] <- ___

# Add new element

___[___] <- ___

# Output modified list

___

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