How to check if a vector contains a given value in R?

Simple Methods

• %in% Operator:

  my_vec <- c(1, 2, 3, 4, 5)
  3 %in% my_vec  # Returns TRUE
  6 %in% my_vec  # Returns FALSE

  This straightforward approach checks if each element on the left-hand side is present in the vector on the right-hand side and returns TRUE or FALSE accordingly.

• any() with Logical Condition:

  any(my_vec == 3)  # TRUE
  any(my_vec == 6)  # FALSE

  This expression evaluates to TRUE if at least one element in my_vec equals the specified value.

Which Approach to Use?

• Use %in% when you want to check membership against multiple values (e.g., c(3, 4) %in% my_vec gives element-wise Boolean results).
• Use any() when you just want a single TRUE or FALSE answer to whether at least one match exists.

Additional Resources
If you’re looking to broaden your coding skill set—beyond quick checks like these and into broader data manipulation or interview prep—consider:

• Grokking the Coding Interview: Patterns for Coding Questions, perfect for mastering common coding challenges and patterns.
• Grokking Data Structures & Algorithms for Coding Interviews, great for honing core algorithmic skills.

For insights into large-scale systems, explore Grokking System Design Fundamentals. And if you’d like expert feedback on your coding or design approach, Coding Mock Interviews with ex-FAANG engineers can supercharge your preparation. Finally, check out the DesignGurus.io YouTube channel for more tips and tutorials.