dplyr: pivots, data types, and importing data

Lecture 10?

Dr. Elijah Meyer

NC State University
ST 295 - Spring 2025

2025-02-13

Checklist

– Have you cloned the today’s AE repo?

– Are you keeping up with prepare material?

– Homework-2 is graded!

– No Quiz this week

Announcements

Thank you for providing feedback on Quiz-4!

– basic ML models like regression, classification

– wrangling data in an efficient and reproducible way

– regression analysis and hypothesis testing

– using tidyverse for data analysis

– improve data visualization skills

Announcements

We have an exam soon (Feb-20th)

Exam-1 is worth 20% of your grade, split equally between

– In-class exam

– Take-home exam

In-class exam

– Closed computer

– Bring handwritten 8x11 sheet of paper (front and back)

Types of questions

– Multiple choice; True False; Short answer; Fill in the blank

– Plot critiques

– What would code produce

Questions?

Take-home exam

– Think about this as a more involved homework

– Questions geared towards applying what we have learned

– Extension question that pushes you to explore something new

Questions?

Homework-2

library(palmerpenguins)

mean_bill <- penguins |>
  summarise(mean_bl = mean(bill_length_mm))

mean_bill # this is unnecessary 

Homework-2

penguins |> # short comments to explain code are very helpful
  summarise(mean_bl = mean(bill_length_mm, na.rm = T)) # and a very good habit

# but we want to make sure that we don't put a large amount of text as a comment. The nice thing about Quarto is that is renders together text, code, and output. Any text that isn't a helpful quick code comment should go outside of our code chunk

Warm-up

What are Wide data? What are Long data?

Warm-up

What are Wide data? What are Long data?

– Wide data contains values that do not repeat in the first column

– Long data contains values that do repeat in the first column

pivot_wider

pivot_wider

– Making tables for quick comparison / display purposes

– names_from

– values_from

AE