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Functions and apply

Define functions with function, default arguments, return a list, and apply a function to every element with sapply and lapply.

Runs in Zerethon IDE · R 4.5 Official R documentation ↗
main.R 
greet <- function(name, greeting = "Hello") {
  paste0(greeting, ", ", name, "!")
}

stats <- function(numbers) {
  list(low = min(numbers), high = max(numbers), mean = mean(numbers))
}

print(greet("Ada"))
print(greet("Linus", greeting = "Hi"))
s <- stats(c(4, 8, 6))
cat(sprintf("%g %g %g\n", s$low, s$high, s$mean))

square <- function(x) x * x
print(square(1:4))
print(sapply(1:3, function(n) n * 10))
print(vapply(c("a", "bb", "ccc"), nchar, integer(1), USE.NAMES = FALSE))
print((\(x) x + 1)(9))

Output

[1] "Hello, Ada!"
[1] "Hi, Linus!"
4 8 6
[1]  1  4  9 16
[1] 10 20 30
[1] 1 2 3
[1] 10
  • A function returns the value of its last expression; return() is only needed to leave early.
  • Return several values in a named list and read them with $.
  • Most built-in functions already work on whole vectors, as square(1:4) does — reach for sapply only when they do not.
  • \(x) x + 1 is a short way to write function(x) x + 1.

Related topics

Official references