Loops

When you need to do something over and over, loops are your friend. R gives you for loops and while loops. But R also has a secret weapon — vectorized operations that often let you skip loops entirely. Let's look at all three approaches.

for Loops

A for loop repeats code for each element in a vector or list. You give it a temporary variable that takes on each value one by one.

fruits <- c("apple", "banana", "cherry")

for (fruit in fruits) {
  print(paste("I like", fruit))
}

# Loop over a sequence of numbers
for (i in 1:5) {
  print(i * 2)
}

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while Loops

A while loop keeps going as long as a condition is true. Be careful — if the condition never becomes false, you'll get an infinite loop!

count <- 1

while (count <= 5) {
  print(paste("Count is", count))
  count <- count + 1
}

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Avoiding Loops with Vectorization

R is built for vectorized operations — they're faster and cleaner than loops. Instead of looping through each element, you can operate on the whole vector at once. This is the R way.

numbers <- 1:10

# Loop approach
squared_loop <- numeric(10)
for (i in 1:10) {
  squared_loop[i] <- numbers[i] ^ 2
}

# Vectorized approach — much simpler!
squared_vec <- numbers ^ 2

print(squared_vec)

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🧪 Quick Quiz

What is the R way of saying 'avoid loops when possible'?

← If & Else

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