Exercises – Markdown (Introduction to R)

Author

Affiliation

Jürgen Wilbert

University of Münster

Task 1

• Using mtcars, select all cars with
  
• more than 6 cylinders (cyl > 6) and
  
• mileage below 20 (mpg < 20).

Task 2

• Using mtcars, sort the cars by
  
• descending horsepower (hp), and
  
• ascending weight (wt).

Task 3

• From mtcars, select only the variables mpg, cyl, hp, and wt.

Task 4

• Using mtcars, create a new variable power_to_weight = hp / wt.

Task 5

• Using mtcars, compute per number of cylinders (cyl)
  
• the mean mileage (mpg), and
  
• the number of cars.

Task 6

Write a single dplyr pipeline that

1. keeps only cars with automatic transmission (am == 0),
   
2. groups the data by cyl,
   
3. computes the mean horsepower (hp),
   
4. arranges the result by descending mean horsepower.

Task 7

• Using starwars, select all characters who
  
• are human, and
  
• have a known height.
  
• Keep only the variables name, height, and mass.
  
• Store the result in human_characters.

Task 8

• Using starwars, create a new variable bmi = mass / (height / 100)^2
  
• Ignore rows with missing height or mass.
  
• Store the result in starwars_bmi.

Task 9

• Using starwars, compute per species
  
• the mean height, and
  
• the number of characters.
  
• Remove species with fewer than 3 characters.

Task 10

Write a single dplyr pipeline that

1. keeps only characters with known gender and mass,
   
2. groups the data by gender,
   
3. computes the median mass per gender,
   
4. keeps only genders with a median mass above the overall median mass,
   
5. returns a tidy summary table.
   
6. Store the result in gender_mass_summary.