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ifelse()

ifelse asks the same yes-or-no question about every item in a list and picks one of two answers for each. It is like a teacher marking a whole class pass or fail in one go.

In this page:

  1. ifelse()
Syntax
r 
result <- ifelse(condition, value_if_true, value_if_false)

ifelse()

ifelse(condition, yes, no) is a vectorized version of if/else, evaluating a condition element-wise across a whole vector and returning a vector of results.

This avoids writing a loop to apply conditional logic to every element. It's one of R's most common idioms for transforming data based on a condition.

Note: Use ifelse() when you need to apply a condition across an entire vector at once, not just a single value.

Example: ifelse()

markup 
scores <- c(95, 60, 78, 40, 88)

results <- ifelse(scores >= 70, "Pass", "Fail")
print(results)
Related Topics

if / else · for Loop · while Loop · repeat

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Common Mistakes
  1. Using if on a whole vector when ifelse() is needed for element-wise results.
  2. Expecting ifelse() to keep the types of both branches, when the result takes a type based on the test and the chosen values.
  3. Forgetting that a NA in the test gives NA in the result.
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