Logical Indexing

Logical Indexing

A vector can be indexed with a logical vector of the same length, selecting only the elements where the corresponding value is TRUE. This is commonly built from a comparison, like v[v > 5], to filter a vector based on a condition. Logical indexing is one of R's most powerful and frequently used idioms.

Note: v[v > 5] reads almost like English: "give me the elements of v that are greater than 5".

Example: Logical Indexing

v <- c(2, 8, 5, 10, 3)

print(v > 5)
print(v[v > 5])

evens <- v[v %% 2 == 0]
print(evens)