R: if vs ifelse

if_ifelse.md

R: if vs ifelse

Inspired by a question about when to use if vs ifelse

First we'll make a simple function that determines whether or not someone is awesome:

is_awesome <- function(name) {
  name %in% c("Heather", "Andy", "Steph", "Jon")
}

Test the function:

is_awesome("Jon")

## [1] TRUE

is_awesome("Heathcliff")

## [1] FALSE

is_awesome(c("Steph", "Heather", "Cuthbert"))

## [1]  TRUE  TRUE FALSE

The if function is designed to work with things that are length 1, like a single name:

if (is_awesome("Heather")) {
  print("Yay")
} else {
  print("Boo")
}

## [1] "Yay"

If we try to use if and else with things that are longer than one, we get a warning, and an unexpected answer:

if (is_awesome(c("Andy", "Heather", "Steph", "Jon", "Bill"))) {
  print("Yay")
} else {
  print("Boo")
}

## Warning in if (is_awesome(c("Andy", "Heather", "Steph", "Jon", "Bill"))) {:
## the condition has length > 1 and only the first element will be used

## [1] "Yay"

If we want to work with vectors that are length > 1, use ifelse

ifelse(is_awesome(c("Andy", "Heather", "Steph", "Jon", "Bill")), "Yay", "Boo")

## [1] "Yay" "Yay" "Yay" "Yay" "Boo"

Sincerely thank you for this!