Working with multiple data frames

Lecture 6

Dr. Elijah Meyer

Duke University
STA 199 - Spring 2023

February 1st, 2023

Checklist

– Clone ae-05

– Make sure you are keeping up with Preperation Videos

– If you need to turn HW in late, see late policy

– If you have extenuating circumstances (see syllabus), contact Ed.

Announcements

Videos

– Requesting videos for missed classes

Homework + Labs

– Late work policy

– Drop 1

Announcements

Exam

– February 10th

– Take home

– Open Notes / Internet / etc

Exam

– Coding + Short answer questions

– Extension questions

– Can NOT be late

– Pull -> Commit -> Push after every question

Announcements

Updates to deadlines

– More time for labs (1 week: Tuesday -> Tuesday)

– Homework (1 week: Wednesday -> Wednesday)

– Subject to change around Exam time / holiday / etc

Announcements

– A lot of errors happen when coding (and that’s okay)

Warm Up

Glimpse mtcars if you need to refamilarize yourself with these data

mtcars |>
  summarize(mean_mpg = mean(mpg))
  
---------------------------------
mtcars |>
  mutate(cyl = factor(cyl)) |>
  group_by(cyl) |>
  summarize(mean_mpg = mean(mpg))

Warm Up

library(tidyverse)
mtcars |>
  summarize(mean_mpg = mean(mpg))

  mean_mpg
1 20.09062

mtcars |>
  mutate(cyl = factor(cyl)) |>
  group_by(cyl) |>
  summarize(mean_mpg = mean(mpg))

# A tibble: 3 × 2
  cyl   mean_mpg
  <fct>    <dbl>
1 4         26.7
2 6         19.7
3 8         15.1

Goals

– Understand join functions

– Join multiple data frames

Motivation

Messy data

– The sheer volume of information is sometimes referred to as “messy” data, because it’s hard to make sense of it all.

Messy data

How?

Joining datasets

Data merging is the process of combining two or more data sets into a single data set. Most often, this process is necessary when you have raw data stored in multiple files, worksheets, or data tables, that you want to analyze together.

Joining datasets

– Left Join

– Inner Join

– Right Join

– Full Join

Joining datasets

AE-05

Clone ae-05

Recap of AE

– This is important! Data are messy!

– Think carefully about the join you use