Design of everyday functions

Transcript

1. The DESIGN 
 of EVERYDAY 
 FUNCTIONS Hadley Wickham
 @hadleywickham


   RStudio September 2018

2. Practitioner Programmer

3. Interactive Easily detect & resolve problems Packaged In production You

   hear your code Things break and people at you Practitioner Programmer

4. Notebook IDE https://yihui.name/en/2018/09/notebook-war/ The First Notebook War Data analyst Engineer

5. Me You Practitioner Programmer

6. Code is a conversation Ambiguity can be tolerated early and

   often Practitioner Programmer Implicit Explicit

7. Practitioner Programmer Implicit Explicit

8. What makes a good door? https://99percentinvisible.org/article/norman-doors

9. None

10. “When you have trouble with things—whether it’s figuring out whether

    to push or pull a door or the arbitrary vagaries of the modern computer and electronics industries—it’s not your fault. Don't blame yourself: blame the designer...” — Donald A. Norman

11. https://twitter.com/irismwang/status/994349937944158208

12. https://twitter.com/BrockTibert/status/1009543843690278920

13. https://twitter.com/mattfrost/status/768078660200898560

14. https://twitter.com/gshotwell/status/675344503566417921

15. https://twitter.com/PetrelStation/status/1038043993387552768

16. https://twitter.com/NateApathy/status/1030263775205707776

17. https://twitter.com/scottmccain5/status/986275394692272129

18. “Rule of thumb: if you think something is clever and

    sophisticated, beware — it is probably self-indulgence.” — Donald A. Norman

19. WAT makes a bad function? https://www.destroyallsoftware.com/talks/wat

20. c(factor("a"), factor("b")) What happens when you combine two factors?

21. c(factor("a"), factor("b")) #> [1] 1 1 What happens when you

    combine two factors? WAT!

22. today <- as.Date("2018-09-18") lunch <- as.POSIXct("2018-09-18 12:00", tz = "Europe/Belgrade")

    c(today, lunch) What happens when you combine a date and a date-time?

23. today <- as.Date("2018-09-18") lunch <- as.POSIXct("2018-09-18 12:00", tz = "Europe/Belgrade")

    c(today, lunch) #> [1] "2018-09-18" #> [2] "4210927-01-24" What happens when you combine a date and a date time? WAT!

24. today <- as.Date("2018-09-18") lunch <- as.POSIXct("2018-09-18 12:00", tz = "Europe/Belgrade")

    c(lunch, today) What happens when you combine a date and a date-time?

25. today <- as.Date("2018-09-18") lunch <- as.POSIXct("2018-09-18 12:00", tz = "Europe/Belgrade")

    c(lunch, today) #> [1] "2018-09-18 12:00:00 CDT" #> [2] "1969-12-31 22:56:32 CST" What happens if you touch a date-time the wrong way? WAT!

26. lunch <- as.POSIXct("2018-09-18 12:00", tz = "Europe/Belgrade") lunch #> [1]

    "2018-09-18 12:00:00 CEST" c(lunch) c(NULL, lunch) What happens if you look at a date-time the wrong way?

27. lunch <- as.POSIXct("2018-09-18 12:00", tz = "Europe/Belgrade") lunch #> [1]

    "2018-09-18 12:00:00 CEST" c(lunch) #> [1] "2018-09-18 05:00:00 CDT" c(NULL, lunch) #> [1] 1537264800 What happens if you look at a date-time the wrong way? WAT! WAT!!

28. What makes a good function? one aspect of ^

29. c(<factor>, <factor>) -> <integer> c(<datetime<tz>>) -> <datetime> c(NULL, <datetime<tz>>) ->

    <double> Types can give us a high-level overview of a function I’ll put types in angle brackets to make clear that this is not real R code

30. To do that we need to review some foundations Atomic

    Numeric Logical Integer Double Character

31. c(<logical>, <logical>) -> <logical> c(<logical>, <integer>) -> <integer> c(<logical>, <double>)

    -> <double> c(<logical>, <character>) -> <character> c(<integer>, <logical>) -> <logical> c(<integer>, <integer>) -> <integer> c(<integer>, <double>) -> <double> c(<integer>, <character>) -> <character> c(<double>, <logical>) -> <double> c(<double>, <integer>) -> <integer> c(<double>, <double>) -> <double> c(<double>, <character>) -> <character> For atomic vectors, the rules are simple

32. For atomic vectors, the rules are simple Logical Integer Double

    Character Logical logical integer double character Integer integer integer double character Double double double double character Character character character character character

33. For atomic vectors, the rules are simple Logical Integer Double

    Character Even if you’re never explicitly learned this, I think you internalise it quickly.

34. Unfortunately c() breaks down when we get to S3 vectors

    Atomic Numeric Logical Integer Double Character factor POSIXct Date S3 vectors

35. Figuring out the rules is the goal of the vctrs

    package http://vctrs.r-lib.org

36. mutate(<data.frame>) -> <data.frame> filter(<data.frame>) -> <data.frame> select(<data.frame>) -> <data.frame> arrange(<data.frame>)

    -> <data.frame> summarise(<data.frame>) -> <data.frame> group_by(<data.frame>) -> <grouped_df> The types of the primary dplyr functions are simple

37. if_else(<logical>, <integer>, <integer>) -> <integer> if_else(<logical>, <double>, <double>) -> <double>

    if_else(<logical>, <integer>, <logical>) -> ??? if_else(<logical>, <integer>, <double>) -> ??? if_else(<logical>, <factor>, <character>) -> ??? if_else(<logical>, <date>, <datetime>) -> ??? But there are a few that are more complex

38. x <- runif(6) if_else(x > 0.5, x, NA) #> Error:

    `false` must be type double, #> not logical Which leads to this annoyance

39. x <- runif(6) if_else(x > 0.5, x, NA) #> Error:

    `false` must be type double, #> not logical if_else(x > 5, x, NA_real_) #> [1] NA 0.700 0.557 NA NA NA Which leads to this annoyance You’re currently forced to learn about the “typed” NAs

40. if_else(<logical>, <integer>, <logical>) -> vec_c(<integer>, <logical>) -> <integer> if_else(<logical>, <factor>,

    <character>) -> vec_c(<factor>, <character>) -> <error> I think I'm starting to see the principles

41. Fin

42. Practitioner Programmer Implicit Explicit Interactive Easily detect & resolve problems

    Packaged In production Code is a conversation Ambiguity can be tolerated early and often

43. https://adv-r.hadley.nz/vectors-chap.html http://vctrs.r-lib.org https://www.destroyallsoftware.com/talks/wat https://99percentinvisible.org/article/norman-doors WAT! http://bit.ly/everyday-functions