Vector Operations

Vectors are cool on their own, but the real magic happens when you start operating on them. R is built for vectorized operations — instead of looping through each element, you can apply an operation to the whole vector at once. It's faster, cleaner, and way more readable.

Vectorized Arithmetic

Add, subtract, multiply, divide — do it to a vector and R applies it to every element. Two vectors of the same length? R pairs them up element by element.

prices <- c(10, 20, 30)

# Add tax to every item at once
prices * 1.08

# Two vectors, element-wise
quantities <- c(2, 5, 3)
prices * quantities

Recycling — When Lengths Don't Match

What if one vector is shorter than the other? R doesn't panic — it "recycles" the shorter one, repeating it as many times as needed. You get a warning if the longer length isn't a multiple of the shorter length.

a <- c(1, 2, 3, 4, 5, 6)
b <- c(10, 20)

# b becomes c(10, 20, 10, 20, 10, 20)
a + b

Filtering with Conditions and which()

Want to find all scores above 80? Just write scores > 80 and R returns a logical vector. Use that to filter. The which() function gives you the indices where a condition is true. And %in% checks membership.

scores <- c(72, 88, 91, 65, 84)

# Logical comparison
scores > 80

# Filter directly
scores[scores > 80]

# Find positions
which(scores > 80)

# Check membership
"Alice" %in% c("Bob", "Charlie", "Alice")