Grammar of data wrangling

Lecture 5

Dr. Benjamin Soltoff

Cornell University
INFO 2950 - Spring 2024

February 6, 2024

Announcements

Announcements

• Suggested solutions posted for ae-01 and ae-02
• Homework 01 due tomorrow night by 11:59pm
• Complete the team team matching survey by 11:59pm tomorrow
• Ask course questions on GitHub Discussion

Clarification for hw-01

Home age variable

tompkins <- tompkins |>
  mutate(home_age = if_else(year_built < 1960, "Before 1960", "Newer than 1960"))

1

Create a new column of data

2

Save the modified data frame as tompkins

Ordering of health categories

brfss <- brfss |>
  mutate(
    general_health = as.factor(general_health),
    general_health = fct_relevel(general_health, "Excellent", "Very good",
                                 "Good", "Fair", "Poor")
  )

1

Modify a column of data

2

Ensure specific ordering of general_health when plotted

3

Save the modified data frame as brfss

Coding style + workflow

• Avoid long lines of code

  • We should be able to see all of your code in the PDF document you submit.

• Label code chunks

  • Do not put spaces in the code-chunk labels.

• Use the tidyverse style guide and styler

• Render, commit, and push regularly

  • Think about it like clicking to save regularly as you type a report

Why data wrangling matters

Application exercise

College education

Source: Cornell stock photography

ae-03

• Go to the course GitHub org and find your ae-03 (repo name will be suffixed with your GitHub name).
• Clone the repo in RStudio Workbench, open the Quarto document in the repo, and follow along and complete the exercises.
• Render, commit, and push your edits by the AE deadline – end of tomorrow.

Recap of AE

• The pipe operator, |>, can be read as “and then”.
• The pipe operator passes what comes before it into the function that comes after it as the first argument in that function.

sum(1, 2)

[1] 3

1 |> 
  sum(2)

[1] 3

• Always use a line break after the pipe, and indent the next line of code.
  • Just like always use a line break between layers of ggplots, after +, and indent the next line.
• Use dplyr functions to transform your data

Some artwork