What is the difference between require() and library() in R?

Both require() and library() load R packages into your current session, but they behave slightly differently in terms of error handling and return values.

Key Distinctions

• library()

  • Throws an error if the package is not found.
  • Commonly used for interactive sessions, scripts, and packages you absolutely need to have loaded.
  • Typically you’ll see library(ggplot2) at the start of many R scripts.

• require()

  • Returns a logical value (TRUE/FALSE) indicating success or failure.
  • If the package can’t be loaded, it only gives a warning rather than a fatal error, and the function call returns FALSE.
  • Often used inside functions or conditional statements, so code can continue gracefully even if the package isn’t found.

Example

# library() usage:
library(ggplot2)
# If ggplot2 is not installed, this throws an error and stops execution.

# require() usage:
if (!require(ggplot2)) {
  warning("Package ggplot2 not available, proceeding without it.")
}
# If ggplot2 is not installed, it prints a warning and returns FALSE instead of stopping.

The choice between library() and require() depends on whether your code should halt on missing packages or handle such cases more flexibly.

Further Learning

• If you’re strengthening your overall coding skills, check out Grokking the Coding Interview: Patterns for Coding Questions.
• For more advanced data manipulation concepts, explore Grokking Data Structures & Algorithms for Coding Interviews.
• Interested in designing scalable, robust systems? Start with Grokking System Design Fundamentals.

You can also polish your interview skills with a Coding Mock Interview led by ex-FAANG engineers, and dive into more tutorials on the DesignGurus.io YouTube channel.