This document discusses reactive programming with R and using Reactlog to better understand reactivity in Shiny apps. It provides an overview of reactive programming concepts like reactive sources, conductors, and endpoints. It also explains what Reactlog is and how it can be used to track the execution of reactive objects in a Shiny app over time, visualizing the life cycle and dependencies between different reactive elements. Installing and using Reactlog to debug reactivity is also covered. The document aims to help readers who are intermediate Shiny users gain a better understanding of reactive programming.

1. 서희(hui.seo@gmailcom)
Reactive Programming with R
(Reactlog로 Shiny 깊게 이해하기)

2. 서희
LG전자 데이터분석가,
챗봇 PM, CRM
hui.seo@gmail.com

3. Reactive Programming
Shiny Reactivity
Reactlog in Shiny
이번 세션은…
오늘 데이터 분석 이야기는 없어요 ;-)
주제는 R의 Shiny & Reactive Programming
Shiny 중급자 == Reactive Programming 이해자

4. Reactive Programming
Shiny Reactivity
Reactlog in Shiny
1시간 뒤에는…

5. Shiny
https://gallery.shinyapps.io/01_hello/

6. Shiny
https://gallery.shinyapps.io/01_hello/

7. Shiny 화면구조
https://gallery.shinyapps.io/01_hello/
Input
(UI.R)
Output
(Server.R)

8. Input (UI.R) Output (Server.R)
Shiny 모듈구성

9. Input (UI.R) Output (Server.R)
Shiny 장점
Front End Back End
User Input Event 처리 X
반복 계산 결과를 Caching

10. Output (Server.R)
Shiny 이벤트 처리
Back End
User Input Event를
처리한다는 것은..

11. http://blog.mclain.ca/
Callback Hell
User/IO Event 처리를 위해
CallBack을 사용했던 시절
“누구로부터 왔고 어디로 가야하는가?”

12. Input (UI.R) Output (Server.R)
Shiny 장점(Again)
Front End Back End
User Input Event 처리 X
반복 계산 결과를 Caching

13. Shiny & 데이터 분석가
데이터 분석가에게 분석과 시각화
집중 할 수 있도록 해줌

14. Shiny & AdminLTE
https://adminlte.io/themes/AdminLTE/index2.html

15. Shiny (But..)
Dashboard의 기능/시각화 복잡도↑
개발/유지 보수 난이도↑

16. Shiny is Reactive
이벤트 처리 구조
“Reactivity”
디버깅 효율화
“Reactlog”
“R Shiny 중급자 이상이 되려면 Reactive Programming 이해필요”

17. Reactive Programming with R
https://shiny.rstudio.com/articles/
Rstudio Site에 있는
Shiny Article
“Backend is Reactive Programming”

18. What is Reactive
Programming?

19. Reactive Manifesto
https://medium.com/data-engineering/reactive-machine-learning-3035b83d18e9
사용자
오류
이벤트
확장성

20. Z에서 출력되는 값은?
X <- 10
Y <- 20
Z <- X + Y
X <- 11
Y <- 22
Print(Z)
https://www.slideshare.net/jongwookkim/ndc14-rx-functional-reactive-programming
NonReactive Programming Reactive Programming

21. 데이터/이벤트 기반 프로그래밍
X <- 10
Y <- 20
Z <- X + Y
X <- 11
Y <- 22
Print(Z)
https://www.slideshare.net/jongwookkim/ndc14-rx-functional-reactive-programming
“순차적 Control Flow” “동시적 Data Flow”

22. RShiny

23. Before Reactivity
“Side Effect in Programming”
https://www.slideshare.net/sefftinge/functional-programming-with-xtend

24. Side Effect in Programming
X = 2
함수1 호출
X = 2
X = 2
함수2 호출
X = 4
1) 함수가 함수 자신의 범위(Scope) 밖에서 영향을 주는 경우
2) 함수는 결과를 반환하지 않을 수 있음
Side Effect

25. Side Effect in R
https://cdn.rawgit.com/jcheng5/user2016-tutorial-shiny/master/slides.html

26. Side Effect in Shiny R
https://cdn.rawgit.com/jcheng5/user2016-tutorial-shiny/master/slides.html
1) 함수가 함수 자신의 범위(Scope) 밖에서 영향을 주는 경우
2) 함수는 결과를 반환하지 않을 수 있음

27. Not Side Effect in R
https://cdn.rawgit.com/jcheng5/user2016-tutorial-shiny/master/slides.html

28. Reactivity – An Overview
X,Y(UI’s event) Z (Rendering Plot)

29. Basic Object

30. Hello Shiny
https://gallery.shinyapps.io/01_hello/

31. Multiple Endpoint

32. Reactive Conductor

33. Reactive Conductor (Cont’)
currentFib

34. Reactive & Non Reactive

35. Implementation of Reactive Object
Reactive value : “input” 웹브라우저를 통한 ui 입력
Reactive Expression :
데이터 베이스 접근, 파일읽기, 오래걸리는 연산
Observer : “output” renderXX의 할당 연산자 오퍼랜드

36. Stop reactions with isolate()
https://shiny.rstudio.com/gallery/actionbutton-demo.html

37. Stop reactions with isolate (Cont’)

38. Stop reactions with isolate (Cont’)

39. Stop reactions with isolate (Cont’)

40. Stop reactions with isolate (Cont’)

41. Execution scheduling

42. Execution scheduling

43. Execution scheduling

44. Execution scheduling

45. An app with reactive conductors

46. An app with reactive conductors

47. An app with reactive conductors

48. An app with reactive conductors

49. An app with reactive conductors

50. An app with reactive conductors

51. An app with reactive conductors

52. An app with reactive conductors

53. ReactLog
History(log) of all reactive interaction
within a shiny application

54. Reactive Programming
- Reactive Source
- Reactive Conductor
(Expression)
- Reactive Endpoint
Reactive
Source
Reactive
expression
Reactive
Endpoint

55. What is reactlog?
• Reactive log를 전/후 시점으로 동작을 추적
• 정의된 Reactive Object 검색 가능
• Cytoscape.js로 구현
설치방법
실행방법

56. reActivity Being Recorded
• Reactivity
• Reactive 객체정의
• Invalidating reactive 객체의 시작/종료
• Isolating reactive 객체의 시작/종료
• Reactive 의존성 추가/삭제
• Value
• Value의 변화
• 연산의 시작과 끝
• Extra
• 사용자 체크 지점의 연산 시간
• Shiny Idle

57. Reactive Life Cycle in Reactlog
The reactive element has finished executing. For
reactive conductors (such as the result
of reactive()), a calculated value is available.
The reactive element has started executing. During
calculation, direct dependencies will be added.
This is the opposite of calculating, the reactive element is
resetting it’s value and removing all direct dependencies.
The reactive element has been reset and is waiting to
calculate.
A visual display of a frozen reactiveVal key. These elements
behave as if their execution is done with req(FALSE).

58. Reactive Life Cycle in Reactlog
A Session Begins

59. Reactive Life Cycle in Reactlog
Execution begins

60. Reactive Life Cycle in Reactlog
Reading a reactive expression

61. Reactive Life Cycle in Reactlog
Reading an input

62. Reactive Life Cycle in Reactlog
Reactive expression completes

63. Reactive Life Cycle in Reactlog
Observer completes

64. Reactive Life Cycle in Reactlog
The next observer executes

65. Reactive Life Cycle in Reactlog
Execution completes, outputs flushed

66. Reactive Life Cycle in Reactlog
An input changes

67. Reactive Life Cycle in Reactlog
Notifying dependents

68. Reactive Life Cycle in Reactlog
Removing relationships

69. Reactive Life Cycle in Reactlog
Re-execution

70. Reactlog UI Menu
Status Bar
Progress Bar
Current step

71. Reactive Life Cycle in Reactlog

72. Reactive Life Cycle in Reactlog

73. Reactive Programming
Shiny Reactivity
Reactlog in Shiny
마무리하며…
Shiny

74. - Shiny Reactlog : https://rstudio.github.io/reactlog/articles/reactlog.html
- Rstudio::Conf 2019 Reactlog 2.0: Debugging the state of Shiny - Barret Schloerke :
https://resources.rstudio.com/rstudio-conf-2019/reactlog-2-0-debugging-the-state-of-shiny
- Effective reactive programming : https://www.rstudio.com/resources/videos/effective-reactive-
programming/
- Shiny Rstudio article : https://shiny.rstudio.com/articles/understanding-reactivity.html
참고문헌