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Defensive R Programming

Colin Gillespie

Jumping Rivers

I don't know about you...

Code that is obvious today
Is often a lot less obvious in a few weeks times

Comments

You can add comments to your R code via #
It turns out that writing good comments is tricky!

# This is a comment
# The above comment isn't very helpful
# Or is it?

Tip 1: Avoid obvious comments

What's obvious is sometimes hard to decide
- For example, the comments
```
 # Loop through data sets
 for (dataset in datasets) {
  # Read in data set
  r <- read.csv(dataset)
 }
```
  look reasonable
- But are perhaps a little too obvious

Tip 2: Avoid comments that you will never update

The most common example is header comments at the top of the file

# Last updated: 1967-02-25
# Author: D Law
# Status: No 1

These sorts of comments are almost never updated
I once saw # list of packages used: XXX, YYY

Tip 3: Be consistent

Always start with a single # or double ##
Start with a capital letter - follow the rules of grammar
Be careful with jokes
- What you find funny, others may take offense
Be sure to comment on code that "looks wrong"
Use # TODO or # XXX to indicate a future problem

Let's practice

Defensive R Programming

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