Indexing in Vectors

Great! Now you understand how to create a vector and assign names to its values.

To access specific elements within a vector, you can use indices. The index of the first element is 1, the second element is 2, and so on. To retrieve the n-th element from a vector vec, use the syntax vec[n]. Additionally, if the vector elements have assigned names, you can extract the values by their names by enclosing the name in quotes and square brackets.

Now, let’s revisit the grades example:

We'll extract the grade for Math and the grade for Literature.

grades <- c(80, 75, 95, 100) # Vector of grades

# Assign names to values of grades

names(grades) <- c('Math', 'Physics', 'English', 'Literature')

# Output the first grade

grades[1]

# Output Literature grade

grades['Literature']


              1234567
            
grades <- c(80, 75, 95, 100) # Vector of grades
# Assign names to values of grades
names(grades) <- c('Math', 'Physics', 'English', 'Literature')
# Output the first grade
grades[1]
# Output Literature grade
grades['Literature']

It's also possible to access multiple elements simultaneously:

grades <- c(80, 75, 95, 100) # Vector of grades

# Assign names to values of grades

names(grades) <- c('Math', 'Physics', 'English', 'Literature')

# Output the second and the third grades

grades[c(2,3)]

# Output Math and Physics grades

grades[c('Math','Physics')]


              1234567
            
grades <- c(80, 75, 95, 100) # Vector of grades
# Assign names to values of grades
names(grades) <- c('Math', 'Physics', 'English', 'Literature')
# Output the second and the third grades
grades[c(2,3)]
# Output Math and Physics grades
grades[c('Math','Physics')]

Tarea

Swipe to start coding

Continuing from the previous exercise, you have a vector named prices with each price assigned to a corresponding item name.

Retrieve the price of 'Armchair' using its name rather than its index.
Retrieve the prices for both the 'Dining table' and 'Dining chair' using their indices.