R Foundations: Debugging, A Hands-On Interactive Course

Code breaks. The skill that separates a beginner from a confident R programmer is what happens next: code that says exactly what went wrong, recovers when it can, and gives you a fast way to find the cause. This three-lesson interactive course builds that skill from the ground up.

Most R tutorials show you the happy path, where every input is clean and every call succeeds. Real data is messier: a value arrives in the wrong type, a file is missing, an API returns nothing. This course is about the unhappy path, and it teaches the two halves of handling it well. First, write code that speaks up clearly when something is off. Second, when an error does happen, find and fix the cause in minutes instead of guessing.

Each lesson is a guided, interactive experience: you run R right in the page, answer checkpoints, and write code as you go. No setup, no installs.

The three lessons

Lesson 1: Errors, Warnings and Messages

R gives you three voices for telling a user something, and they differ by how loudly they interrupt. Use message() to report progress without changing the result, warning() to flag a problem the code can survive, and stop() to halt cleanly when it cannot continue, and learn to write an error message a stranger can actually act on.

Start Lesson 1: Errors, Warnings and Messages

Lesson 2: tryCatch and Input Validation

Catch a failing call with tryCatch and decide what to do instead of letting the whole script crash, then move the defence earlier: guard a function's inputs up front with stopifnot and clear checks so bad arguments are rejected with a helpful message before they cause trouble.

Start Lesson 2: tryCatch and Input Validation

Lesson 3: Debugging Tools in R

When something breaks anyway, find the cause fast. Read a traceback to see the chain of calls that led to the error, pause a running function with browser to inspect its variables in the moment, and use the IDE's debugger to step through code one line at a time.

Start Lesson 3: Debugging Tools in R

Who this is for

You can write a function with arguments and a return value, and you know if and else. That is enough. You do not need any prior experience with error handling. By the end you will write code that reports problems clearly, fails safely when it must, and gives you a quick path to the cause when a bug slips through.

What you will be able to do

• Pick the right signal, message(), warning() or stop(), for a given situation, and write error messages users can act on
• Recover from a failing call with tryCatch instead of crashing the whole run
• Validate a function's inputs with stopifnot so bad arguments fail early and clearly
• Read a traceback to find which call raised an error
• Pause and inspect a running function with browser and the IDE debugger

This course is part of the free New to R foundations track.

Ready? Begin with Lesson 1: Errors, Warnings and Messages.