Intermediate R II: Functions cont’d, iteration, and getting help

Session 8

September 28, 2023

Before we jump in…

Show and tell (Late October)

• An opportunity to apply workshop skills to your own work.
• You could apply different parts to different projects, or more integratively to one single project.
• Optional, but encouraged!

Some inspirations

• Turn the project folder for one of your current research project into a git/GitHub repo and/or R project
• Modify an R script to use functions, conditionals, or best-practices for code formatting
• Improve directory organization for project or your entire computer!

Today’s objectives

• Modify our data cleaning function to apply to different islands
• Use iteration to apply this function to each island
• Organize our workflow into “functions” and “running” scripts
• Learn how to get help with more advanced topics

Part I: Generalizing a function

• Open up your Rproject from Tuesday
• Coding objectives:
  • Make sure the function we wrote works
  • Apply this function to different islands by swapping URLS
  • Add “ifelse” logic to avoid having to re-type the URL every time

Part II: Iteration

Iteration by hand

my_first_site <- read.csv("data_first.csv")
my_second_site <- read.csv("data_second.csv")
my_third_site <- read.csv("data_third.csv")

Why use code to iterate?

• Less code: fewer bugs, easier to understand
• Easier to apply to new situations
• Faster to write, maybe faster to run

Iteration using for loops

• Coding objectives:
  • Write a for loop to apply our cleaning function to each island
  • Store the results in a list
  • Convert this list back to a dataframe

Iteration using purrr::map

• Coding objectives:
  • Use purrr::map as an alternative to a for loop
  • Demonstrate purrr applied to more complex workflows

Part III: Getting help

• See the Getting Help section!

Wrap-up

Commit this week’s work and create a new PR.

Homework

• Identify a section of your code that could be made more efficient using a for loop or iterating using a function
• Start thinking about show-and-tell opportunities!