Reshaping Data

James Normington

Due this Week

  • At least 1 Tidy Tuesday by next Friday!

Learning Goals

  • Understand the difference between wide and long data format and distinguish the case (unit of observation) for a given data set
  • Develop comfort in using pivot_wider and pivot_longer in the tidyr package

Template File

Download a template .Rmd of this activity. Put the file in a Day_08 folder within your COMP_STAT_112 folder.

  • This .Rmd only contains examples and 3 exercises that we’ll work on in class.

Describe to your Neighbor

Everyone: Look at this small data set.

Partner A: Describe the structure of the data set in words.

name sex total
Courtney F 257289
Courtney M 22619
Riley F 100881
Riley M 92789

Describe to your Neighbor

Partner A: Close your eyes.

Partner B: Describe the how the structure of the data set changed. Think of describing “steps” taken.

Partner A: Sketch what you think the new data set looks like.

name F M
Courtney 257289 22619
Riley 100881 92789

Describe to your Neighbor

Partner B: Close your eyes.

Partner A: Describe the how the structure of the data set changed. Think of describing “steps” taken.

Partner B: Sketch what you think the new data set looks like.

name F M ratio
Courtney 257289 22619 0.0879128
Riley 100881 92789 0.9197867
name ratio sex total
Courtney 0.0879128 F 257289
Courtney 0.0879128 M 22619
Riley 0.9197867 F 100881
Riley 0.9197867 M 92789

Wider V. Longer Format

If we want to maintain all of the values in the data set (not collapsing rows with summarize) but have a different unit of observation (or case), we can:

  • Make the data wider by spreading out the values across new variables (e.g. total counts for binary “Male” and “Female” names)
  • Make the data longer by combining values from different variables into 1 variable (take counts for binary “Male” and “Female” names and combine into one total column)

R Functions

pivot_wider()

  • Inputs: data, names_from = var_name, values_from = var_name

pivot_longer()

  • Inputs: data, cols = c(var_name2, var_name2), names_to = “string”, values_to = “string”

R Functions

Taken from tidyr cheatsheet

In Class

Go through the example code in the Rmd file to make sure you understand how we reshape data to be wider and longer.

After Class

  • TT4
  • Assignment 5 due Wed. 2/22 @ 11:59pm

    • Part 1 in Chap 7 (Six Main Verbs)

    • Part 2 in Chap 8 (Reshaping Data)