Matchstick Men: A Serious Case Study in Code Quality

Matchstick Men:
A Serious Case Study in Code Quality
Chris Campbell, PhD
Matchstick Men
Doing Work
• Confirmatory analysis
should be well planned
• Exploratory analysis may
be more investigative
Explore... with R scripts
• What is
possible?
• How should it
be achieved?
What Next? Industrialization!
• Mass
production
• Reduced costs
What Next? Industrialization!
• Mass
production
• Reduced costs
• Reproducibility
• Easier
Quality Control
?
http://www.econometricsbysimulation.com/
Doing Work
draw.stick.R
• low level
plotting function
to add
matchstick men
to plot
Doing Work
draw.stick.R
•
•
•
•
refactored to a function
documented with comments
multipurpose
tested




Identify Units
draw.stick.R
drawStick.R
addHead.R
addArms.R
addLegs.R
Identify Units
• Easier to:
• Test
• Maintain
• Extend
Enhance Documentation
• Describe current behaviour
• Provide examples
• Note intended usage and exceptions
roxygen2
roxygen2
• Awesome tool
• Documenting as you go
along is correct
• Automated checks that
all arguments are
described
roxygen2
• Yes, even you!
Make Package Source
> package.skeleton(name = "stick")
Make Package Documentation
> roxygenize("stick")
Write Tests
• Easier to:
• Check code is correct!
• Keep track of working cases
• Keep track of error cases
• Maintain
• Extend
testthat
• Awesome tool
• Testing as you go along
is correct
• Automatically run all
tests
• See also RUnit
Examine Code
• Code Review:
• Double check code is correct!
• Metrics for code quality
• Ensure that code meets requirements
TestCoverage
> reportCoverage("stick")
• Awesome tool
• View tested components
• Available 2014
functionMap
• Awesome tool
• View relationships
between files
• Available 2014
Quality
•
•
•
•
•
Requirements
Make Code Do Thing
Unit Test Code
Examine Code for Improvements
System Test Code