How to Make a Great R Reproducible Example

Creating a reproducible example, or “reprex,” in R is an essential skill for effective collaboration and problem-solving within the R programming community. A well-crafted reprex allows others to understand, troubleshoot, and improve your code quickly. Here’s a step-by-step guide on how to make a great reproducible example in R.

1. Why Reproducibility Matters

When asking for help or sharing your work, it’s crucial that others can replicate the problem you’re facing. Reproducibility ensures:

• Clear communication: Others understand exactly what you’re working on.
• Efficient troubleshooting: The problem is isolated, making it easier to identify and solve.
• Effective collaboration: Colleagues and community members can contribute solutions.

2. Key Components of a Great Reproducible Example

A good reproducible example should include the following:

a. Minimal Code

Include only the code that’s necessary to reproduce the problem. Stripping away unrelated parts helps keep things clear and avoids distractions.

• Example

# Problematic code
x <- c(1, 2, 3, 4, 5)
y <- x^2
plot(x, y, type = "o")

b. Self-contained Code

Ensure that your example can be run independently. This means including all relevant data, libraries, and variables in the code.

• Bad example (missing libraries or data)

plot(x, y)

• Good example

library(ggplot2)
x <- 1:5
y <- x^2
qplot(x, y)

c. Using Built-in Data or Small Dataframes

Where possible, use built-in datasets (e.g., iris, mtcars) or create small, simple datasets in the example. This keeps the example easy to follow and avoids requiring external files.

• Example

df <- data.frame(
  id = 1:3,
  value = c(10, 20, 30)
)
print(df)

d. State the Expected Outcome

Make it clear what you expect the output to be, and how it differs from what you’re getting.

• Example:

# I expect the plot to show a straight line, but instead it looks exponential.
x <- c(1, 2, 3, 4, 5)
y <- x^2
plot(x, y, type = "l")

e. Add Error Messages or Warnings

If your code produces errors or warnings, include them in your reprex. This gives others insight into what might be going wrong.

• Example:

x <- 1:5
y <- "a"  # This will cause an error
plot(x, y)
# Error message: non-numeric argument to binary operator

3. Tools for Creating Reproducible Examples

Several tools can assist in creating and sharing reproducible examples in R:

a. reprex Package

The reprex package automates the process of making a reproducible example. It renders your R code as clean, shareable output (including formatted error messages and outputs), making it easy to paste into forums or GitHub.

• Install and use

install.packages("reprex")
library(reprex)
reprex({
  x <- 1:5
  y <- x^2
  plot(x, y, type = "o")
})

b. Session Info

Including your session info can help others understand the environment in which your code was run. This can be crucial if your issue is version-specific.

• Example:

sessionInfo()

4. Best Practices for Reprexes

Here are some additional tips to make your example even more effective:

• Use Comments: Add brief comments to explain each section of your code, especially where it relates to the issue.
• Keep it Short: The shorter and simpler, the better. Focus on the problem at hand.
• Test Before Sharing: Run your reprex to ensure it works as intended before sharing it. This avoids wasting others’ time with typos or missing elements.

5. Common Mistakes to Avoid

Here are some pitfalls to watch out for when making a reproducible example:

• Including Too Much Code: Extraneous code makes it harder for others to see the core issue.
• Omitting Libraries or Data: Missing components make your code impossible to run.
• Overcomplicating the Problem: Simplify the code to isolate the issue.

6. Sharing Your Reprex

Once your reproducible example is ready, share it in a format that’s easy to copy and paste. For platforms like GitHub or Stack Overflow, the reprex package helps by formatting the code and output in markdown, making it easy to share.

Conclusion

A well-constructed reproducible example is an invaluable tool for getting help with R code. By providing minimal, self-contained, and clear code, along with any errors or unexpected behavior, you enable others to quickly understand and assist with your problem. With practice, creating reprexes becomes second nature, leading to faster resolutions and better collaboration in the R community.