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WRITING R PACKAGES
PART I
Jeff Goldsmith, PhD
Department of Biostatistics
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When to write packages
“If you have more than two functions, write a
package”
- almost everyone, basically
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In particular, why not just write a lot of functions in scripts or R Markdown code
chunks?
• Documentation reminds you what functions do, what inputs are, and what
outputs are
• Encapsulates code in standard, easy-to-share format
• Checks / tests ensure things are self contained and work as expected
Why to write packages
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Why to write packages
“I wish I could go back in time and create the package the first moment I thought about it,
and then use all the saved time to watch cat videos because that really would have been
more productive.”
“It is about saving yourself time.”
- Hilary Parker, “Writing an R Package from Scratch”
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Why to write packages
“I wish I could go back in time and create the package the first moment I thought about it,
and then use all the saved time to watch cat videos because that really would have been
more productive.”
“It is about saving yourself time.”
- Hilary Parker, “Writing an R Package from Scratch”
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• Collection of related functions, with helpful documentation, written to stand
alone
• Can also include data, vignettes, non-R code (e.g. C++), tests, …
What is a package?
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• Metadata / overview
• Help pages
• Dependencies
• Code
Parts of a bare-bones package
You can edit the DESCRIPTION and the R code yourself, but you should use
other tools to generate the help pages and the NAMESPACE
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With apologies to Hilary …
• Step 0: whatever work you did to get to 2+ functions.
• Step 1: create package skeleton with devtools::create()
• Step 2: add your functions to /R/
• Step 3: add documentation using roxygen comments
• Step 4: iterate
Can also add a README and put on GitHub.
How to write a package
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• Start small:
– Write small functions that do one thing well and interact easily
– Avoid unneeded complexity
– When you have a couple of functions, put them in a package
– Build complexity as needed
• Clarity is better than cleverness
How to write a package
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How to write a package
Jeff Leek’s Guide to Writing R Packages