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']
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')]
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.
Soluzione
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