Data Rectangling

Talk about data rectangling and list-columns at RStudio Conf 2018 in San Diego
https://www.rstudio.com/conference/
Gist of code I showed:
https://gist.github.com/jennybc/3afafce0a06fde314b5c9844912d6bd7

Transcript

1. Data Wrangling
   @JennyBryan
   @jennybc
   
   
   

   View Slide

2. Data Wrangling
   @JennyBryan
   @jennybc
   
   
   Rect
   

   View Slide

3. View Slide

4. View Slide

5. View Slide

6. atomic vectors
   logical factor
   integer, double
   

   View Slide

7. vectors of same length? DATA FRAME!
   

   View Slide

8. vectors don’t have to be atomic
   works for lists too! list column
   

   View Slide

9. name

   
   stuff

   
   this is a data frame!
   a tibble, specifically
   

   View Slide

10. a list
    

    View Slide

11. a homogeneous list
    

    View Slide

12. Why work with lists?
    You have no choice.
    •String processing, e.g., splitting
    •JSON or XML, e.g. web APIs
    •Models, plots, & collections thereof
    

    View Slide

13. An API Of Ice And Fire
    https://anapioficeandfire.com
    https://cran.r-project.org/package=repurrrsive
    

    View Slide

14. "Combines the excitement of iris and mtcars,
    with the complexity of recursive lists.
    W00t!"
    install.packages("repurrrsive")
    

    View Slide

15. https://blog.rstudio.com/2017/08/22/rstudio-v1-1-preview-object-explorer/
    View(YOUR_HAIRY_LIST)
    

    View Slide

16. got_chars[[9]][["name"]]
    got_chars[[9]][["titles"]]
    

    View Slide

17. x[[i]]
    x[i]
    x
    from
    http://r4ds.had.co.nz/vectors.html#lists-of-condiments
    

    View Slide

18. http://blog.codinghorror.com/falling-into-the-pit-o
    pit of success
    

    View Slide

19. https://shibumo.wordpress.com
    gentle hill of striving
    

    View Slide

20. View Slide

21. map(.x, .f, ...)
    purrr::
    

    View Slide

22. map(.x, .f, ...)
    for every element of .x
    apply .f
    

    View Slide

23. map(.x, .f, ...)
    .f has some special shortcuts
    to make common tasks easy
    map(.x, "TEXT")
    map(.x, i)
    

    View Slide

24. .x = minis
    

    View Slide

25. map(minis, "pants")
    

    View Slide

26. go to R
    

    View Slide

27. map_lgl(.x, .f, ...)
    map_int(.x, .f, ...)
    map_dbl(.x, .f, ...)
    map_chr(.x, .f, ...)
    

    View Slide

28. map_dfr(minis, `[`,
    c("pants", "torso", "head")
    

    View Slide

29. If everything is equally easy,
    everything is equally hard.
    paraphrasing David Heinemeier Hansson re: Ruby on Rails
    

    View Slide

30. map(.x, .f, ...)
    .f can take many forms
    • existing function
    • anonymous function
    • formula
    

    View Slide

31. .x = minis
    

    View Slide

32. map(minis, antennate)
    

    View Slide

33. library(glue)
    

    

    glue_data(

    list(name = "Jenny", born = "in Atlanta"),

    "{name} was born {born}."

    )

    #> Jenny was born in Atlanta.
    

    

    glue_data(got_chars[[2]], "{name} was born {born}.")

    #> Tyrion Lannister was born In 273 AC, at Casterly Rock.
    

    glue_data(got_chars[[9]], "{name} was born {born}.")

    #> Daenerys Targaryen was born In 284 AC, at Dragonstone.
    

    View Slide

34. glue_data(got_chars[[9]], "{name} was born {born}.")
    ~ glue_data( .x , "{name} was born {born}.")
    replace your
    example with .x
    prefix with ~ to say
    "it's a formula!"
    

    View Slide

35. map_chr(got_chars, ~ glue_data(.x, "{name} was born {born}."))

    #> [1] "Theon Greyjoy was born In 278 AC or 279 AC, at Pyke."
    #> [2] "Tyrion Lannister was born In 273 AC, at Casterly Rock."
    #> [3] "Victarion Greyjoy was born In 268 AC or before, at Pyke."
    #> [4] "Will was born ."
    #> [5] "Areo Hotah was born In 257 AC or before, at Norvos."
    #> [6] "Chett was born At Hag's Mire."
    #> [7] "Cressen was born In 219 AC or 220 AC."
    #> [8] "Arianne Martell was born In 276 AC, at Sunspear."
    #> [9] "Daenerys Targaryen was born In 284 AC, at Dragonstone."
    drop-in to any member
    of the map_*() family
    

    View Slide

36. name

    
    stuff

    
    this is a data frame!
    a tibble, specifically
    

    View Slide

37. Why put a list into a data frame?
    safety & convenience
    •Manage multiple vectors holistically
    •Use existing toolkit for filter, select, etc.
    

    View Slide

38. What happens in the
    data frame
    Stays in the data frame
    

    View Slide

39. last R example:
    list in a data frame = list-column
    

    View Slide

40. lists are part of life
    RStudio Object viewer helps
    tibbles are list-friendly
    map() functions help you
    compute on & simplify lists
    

    View Slide