Intermediate R II: Iteration and more functions
Session 10
October 1, 2024
Learning objectives
- Write a more advanced function
- Set up an analysis with function and analysis scripts
- Use iteration to streamline workflows involving functions
When should I write my own function?
- Standardized procedures done many times
- Discrete chunks of a workflow
- Code used by multiple scripts or at multiple points in a workflow
When should I leave code in a script?
- Single-use, highly-customized code (e.g. a plot)
- Code that is changing a lot
- Code that tells the story of your analysis
Questions to ask yourself
- Do I find myself typing the same code over and over?
- Am I copy-pasting and changing a single variable/character?
- Does this code distract from the readability of a script?
- Is there an existing function I could pull from an R package?
Coding time
Important
Make sure you are in the right project and on an appropriate branch!
Coding time
- Review sample analysis to decide what could be a function
- Organize this analysis into analysis and function scripts
Iteration
Iteration
- Iteration allows you to repeat the same process many times on different objects.
forloops:- Run sequentially
- Easy to write and read
- Slower, can be inefficient
purrr::map:- Can run in parallel
- Fairly readable
- More efficient
Anatomy of for loops
for(<thing> in <some things>) {
<do something with or to the thing>
}for(i in 1:10) {
print(i^2)
}Storing the output of for loops
Anatomy of purrr::map
Storing the output of purrr::map
Coding time
- Practice using a for loop and a map statement to apply our function to each island in turn.
Resources
- R4DS on iteration
purrrandfurrrdocumentation
Intermediate R II: Iteration and more functions Session 10 October 1, 2024