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Modifying Vectors

Excellent! You now know how to create a vector, name its values, and extract elements from it. The next step we will explore is how to modify a vector by adding new items to it or deleting existing ones.

There are a couple of methods to add a new value to an existing vector. Suppose we have a vector named vec and we wish to append new_value to it, with the name 'new_name' assigned to this new value. The diagram below illustrates both methods.

For instance, let’s apply these methods using the grades example by adding a new grade, 60, for the subject 'Philosophy'. The first method involves utilizing vectors:


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# Vector of grades and names
grades <- c(80, 75, 95, 100)
names(grades) <- c('Math', 'Physics', 'English', 'Literature')
# Add new value using vectors
grades <- c(grades, 60) # Add new value
names(grades)[length(grades)] <- 'Philosophy' # Add name
grades # Output the vector

Now, let’s try the second method where we assign a name to the value as we add it:


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# Vector of grades and names
grades <- c(80, 75, 95, 100)
names(grades) <- c('Math', 'Physics', 'English', 'Literature')

# Add new value 
grades['Philosophy'] <- 60 # Add value with name
grades # Output the vector

Thus, if your vector does not have names, the first method is more appropriate. However, if your vector already has names, the second method is preferable.

With the second method, you can add new values and also reassign existing ones. For example, if you execute grades['Math'] <- 100, the original grade of 80 for Math will be updated to 100. You can achieve the same result by referring to the index, like this: grades[1] <- 100.

Task

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Add a new item named 'Desk' with a price of 135 to the end of the prices vector using the second method (assigning the name while adding the value).
Update the price of the 'Bookshelf' to 180. You can use either the index or the name to do this.
Display the modified vector prices.

Solution

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Section 2. Chapter 8

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Modifying Vectors

For instance, let’s apply these methods using the grades example by adding a new grade, 60, for the subject 'Philosophy'. The first method involves utilizing vectors:


              1234567
            
# Vector of grades and names
grades <- c(80, 75, 95, 100)
names(grades) <- c('Math', 'Physics', 'English', 'Literature')
# Add new value using vectors
grades <- c(grades, 60) # Add new value
names(grades)[length(grades)] <- 'Philosophy' # Add name
grades # Output the vector

Now, let’s try the second method where we assign a name to the value as we add it:


              1234567
            
# Vector of grades and names
grades <- c(80, 75, 95, 100)
names(grades) <- c('Math', 'Physics', 'English', 'Literature')

# Add new value 
grades['Philosophy'] <- 60 # Add value with name
grades # Output the vector

Thus, if your vector does not have names, the first method is more appropriate. However, if your vector already has names, the second method is preferable.

Task

Swipe to start coding

Add a new item named 'Desk' with a price of 135 to the end of the prices vector using the second method (assigning the name while adding the value).
Update the price of the 'Bookshelf' to 180. You can use either the index or the name to do this.
Display the modified vector prices.

Solution

Switch to desktop for real-world practiceContinue from where you are using one of the options below

Everything was clear?

Thanks for your feedback!

Section 2. Chapter 8

Switch to desktop for real-world practiceContinue from where you are using one of the options below