Intro Shiny

class: inverse, center, middle

# <svg aria-hidden="true" role="img" viewBox="0 0 192 512" style="height:1em;width:0.38em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M144 80c0 26.5-21.5 48-48 48s-48-21.5-48-48s21.5-48 48-48s48 21.5 48 48zM0 224c0-17.7 14.3-32 32-32H96c17.7 0 32 14.3 32 32V448h32c17.7 0 32 14.3 32 32s-14.3 32-32 32H32c-17.7 0-32-14.3-32-32s14.3-32 32-32H64V256H32c-17.7 0-32-14.3-32-32z"/></svg> Introduction to Shiny

![:custom_hr]()

---
class: inverse, center, middle

# General introduction

![:custom_hr]()

---
# Shiny applications

## <svg aria-hidden="true" role="img" viewBox="0 0 640 512" style="height:1em;width:1.25em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M208 0C322.9 0 416 78.8 416 176C416 273.2 322.9 352 208 352C189.3 352 171.2 349.7 153.9 345.8C123.3 364.8 79.13 384 24.95 384C14.97 384 5.93 378.1 2.018 368.9C-1.896 359.7-.0074 349.1 6.739 341.9C7.26 341.5 29.38 317.4 45.73 285.9C17.18 255.8 0 217.6 0 176C0 78.8 93.13 0 208 0zM164.6 298.1C179.2 302.3 193.8 304 208 304C296.2 304 368 246.6 368 176C368 105.4 296.2 48 208 48C119.8 48 48 105.4 48 176C48 211.2 65.71 237.2 80.57 252.9L104.1 277.8L88.31 308.1C84.74 314.1 80.73 321.9 76.55 328.5C94.26 323.4 111.7 315.5 128.7 304.1L145.4 294.6L164.6 298.1zM441.6 128.2C552 132.4 640 209.5 640 304C640 345.6 622.8 383.8 594.3 413.9C610.6 445.4 632.7 469.5 633.3 469.9C640 477.1 641.9 487.7 637.1 496.9C634.1 506.1 625 512 615 512C560.9 512 516.7 492.8 486.1 473.8C468.8 477.7 450.7 480 432 480C350 480 279.1 439.8 245.2 381.5C262.5 379.2 279.1 375.3 294.9 369.9C322.9 407.1 373.9 432 432 432C446.2 432 460.8 430.3 475.4 426.1L494.6 422.6L511.3 432.1C528.3 443.5 545.7 451.4 563.5 456.5C559.3 449.9 555.3 442.1 551.7 436.1L535.9 405.8L559.4 380.9C574.3 365.3 592 339.2 592 304C592 237.7 528.7 183.1 447.1 176.6L448 176C448 159.5 445.8 143.5 441.6 128.2H441.6z"/></svg> What is Shiny?

---

# Shiny applications

## What for?

### - apps are cool and can be useful

### - interactive capabilities

### - micro-meso web applications tailored to our needs

## Why not another technology?

### - because it's very powerful

### - because we are <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg> users!
  - you only need to know <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg> (at least for start)
  - design for our community
  - use tools (packages) you already know

---
# Shiny is a package

.pull-left[
### An <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg> package developed by [Posit](https://posit.co/)
[`shiny`](https://cran.r-project.org/package=shiny) .font90[12/2012 (0.2.3) <svg aria-hidden="true" role="img" viewBox="0 0 448 512" style="height:1em;width:0.88em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M438.6 278.6c12.5-12.5 12.5-32.8 0-45.3l-160-160c-12.5-12.5-32.8-12.5-45.3 0s-12.5 32.8 0 45.3L338.8 224 32 224c-17.7 0-32 14.3-32 32s14.3 32 32 32l306.7 0L233.4 393.4c-12.5 12.5-12.5 32.8 0 45.3s32.8 12.5 45.3 0l160-160z"/></svg> 10/2022 (1.7.3)]
]
.pull-right[
.left[[<img src='https://raw.githubusercontent.com/rstudio/shiny/master/man/figures/logo.png'
alt='Siny logo' width='24%' style='vertical-align:middle'>](https://cran.r-project.org/package=shiny)]

]

> [`shiny`](https://cran.r-project.org/package=shiny) makes it incredibly easy to build interactive web applications with R. Automatic "reactive" binding between inputs and outputs and extensive prebuilt widgets make it possible to build beautiful, responsive, and powerful applications with minimal effort.

```R
install.packages("shiny")
library("shiny")
packageVersion("shiny")
[1] ‘1.7.3’
```

* https://github.com/rstudio/shiny/blob/main/NEWS.md

???
I's an R package 
we wont go over details of new feature but important to have latest (minor) version

---
# Shiny is a framework to create apps

.pull-left[
<img src="https://d33wubrfki0l68.cloudfront.net/0c97eee3d8fc820f3a8d670c08b286e8a524257b/e426c/cover.png" alt="" width="80%">

]

.pull-right[
> .font90[Shiny is a framework for creating web applications using R code. It is designed primarily with data scientists in mind, and to that end, you can create pretty complicated Shiny apps with no knowledge of HTML, CSS, or JavaScript.]

* You create the **frontend** and the **backend** with <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg>
]

---
# Backend vs Frontend

- Major distinctions in web applications

* __Frontend__: what you see, refers to the interface

* __Backend__: what's happening on the server (remote computer)

- With Shiny you are using <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg> to create both:

* <svg aria-hidden="true" role="img" viewBox="0 0 576 512" style="height:1em;width:1.12em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M160 256C160 185.3 217.3 128 288 128C358.7 128 416 185.3 416 256C416 326.7 358.7 384 288 384C217.3 384 160 326.7 160 256zM288 336C332.2 336 368 300.2 368 256C368 211.8 332.2 176 288 176C287.3 176 286.7 176 285.1 176C287.3 181.1 288 186.5 288 192C288 227.3 259.3 256 224 256C218.5 256 213.1 255.3 208 253.1C208 254.7 208 255.3 208 255.1C208 300.2 243.8 336 288 336L288 336zM95.42 112.6C142.5 68.84 207.2 32 288 32C368.8 32 433.5 68.84 480.6 112.6C527.4 156 558.7 207.1 573.5 243.7C576.8 251.6 576.8 260.4 573.5 268.3C558.7 304 527.4 355.1 480.6 399.4C433.5 443.2 368.8 480 288 480C207.2 480 142.5 443.2 95.42 399.4C48.62 355.1 17.34 304 2.461 268.3C-.8205 260.4-.8205 251.6 2.461 243.7C17.34 207.1 48.62 156 95.42 112.6V112.6zM288 80C222.8 80 169.2 109.6 128.1 147.7C89.6 183.5 63.02 225.1 49.44 256C63.02 286 89.6 328.5 128.1 364.3C169.2 402.4 222.8 432 288 432C353.2 432 406.8 402.4 447.9 364.3C486.4 328.5 512.1 286 526.6 256C512.1 225.1 486.4 183.5 447.9 147.7C406.8 109.6 353.2 80 288 80V80z"/></svg> Frontend (User interface) 
      * what you will see
      * where inputs and outputs are displayed
      * `ui`: an **object** (a tag list, includes HTML content)

* <svg aria-hidden="true" role="img" viewBox="0 0 640 512" style="height:1em;width:1.25em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M308.5 135.3c7.1-6.3 9.9-16.2 6.2-25c-2.3-5.3-4.8-10.5-7.6-15.5L304 89.4c-3-5-6.3-9.9-9.8-14.6c-5.7-7.6-15.7-10.1-24.7-7.1l-28.2 9.3c-10.7-8.8-23-16-36.2-20.9L199 27.1c-1.9-9.3-9.1-16.7-18.5-17.8C173.7 8.4 166.9 8 160 8s-13.7 .4-20.4 1.2c-9.4 1.1-16.6 8.6-18.5 17.8L115 56.1c-13.3 5-25.5 12.1-36.2 20.9L50.5 67.8c-9-3-19-.5-24.7 7.1c-3.5 4.7-6.8 9.6-9.9 14.6l-3 5.3c-2.8 5-5.3 10.2-7.6 15.6c-3.7 8.7-.9 18.6 6.2 25l22.2 19.8C32.6 161.9 32 168.9 32 176s.6 14.1 1.7 20.9L11.5 216.7c-7.1 6.3-9.9 16.2-6.2 25c2.3 5.3 4.8 10.5 7.6 15.6l3 5.2c3 5.1 6.3 9.9 9.9 14.6c5.7 7.6 15.7 10.1 24.7 7.1l28.2-9.3c10.7 8.8 23 16 36.2 20.9l6.1 29.1c1.9 9.3 9.1 16.7 18.5 17.8c6.7 .8 13.5 1.2 20.4 1.2s13.7-.4 20.4-1.2c9.4-1.1 16.6-8.6 18.5-17.8l6.1-29.1c13.3-5 25.5-12.1 36.2-20.9l28.2 9.3c9 3 19 .5 24.7-7.1c3.5-4.7 6.8-9.5 9.8-14.6l3.1-5.4c2.8-5 5.3-10.2 7.6-15.5c3.7-8.7 .9-18.6-6.2-25l-22.2-19.8c1.1-6.8 1.7-13.8 1.7-20.9s-.6-14.1-1.7-20.9l22.2-19.8zM208 176c0 26.5-21.5 48-48 48s-48-21.5-48-48s21.5-48 48-48s48 21.5 48 48zM504.7 500.5c6.3 7.1 16.2 9.9 25 6.2c5.3-2.3 10.5-4.8 15.5-7.6l5.4-3.1c5-3 9.9-6.3 14.6-9.8c7.6-5.7 10.1-15.7 7.1-24.7l-9.3-28.2c8.8-10.7 16-23 20.9-36.2l29.1-6.1c9.3-1.9 16.7-9.1 17.8-18.5c.8-6.7 1.2-13.5 1.2-20.4s-.4-13.7-1.2-20.4c-1.1-9.4-8.6-16.6-17.8-18.5L583.9 307c-5-13.3-12.1-25.5-20.9-36.2l9.3-28.2c3-9 .5-19-7.1-24.7c-4.7-3.5-9.6-6.8-14.6-9.9l-5.3-3c-5-2.8-10.2-5.3-15.6-7.6c-8.7-3.7-18.6-.9-25 6.2l-19.8 22.2c-6.8-1.1-13.8-1.7-20.9-1.7s-14.1 .6-20.9 1.7l-19.8-22.2c-6.3-7.1-16.2-9.9-25-6.2c-5.3 2.3-10.5 4.8-15.6 7.6l-5.2 3c-5.1 3-9.9 6.3-14.6 9.9c-7.6 5.7-10.1 15.7-7.1 24.7l9.3 28.2c-8.8 10.7-16 23-20.9 36.2L315.1 313c-9.3 1.9-16.7 9.1-17.8 18.5c-.8 6.7-1.2 13.5-1.2 20.4s.4 13.7 1.2 20.4c1.1 9.4 8.6 16.6 17.8 18.5l29.1 6.1c5 13.3 12.1 25.5 20.9 36.2l-9.3 28.2c-3 9-.5 19 7.1 24.7c4.7 3.5 9.5 6.8 14.6 9.8l5.4 3.1c5 2.8 10.2 5.3 15.5 7.6c8.7 3.7 18.6 .9 25-6.2l19.8-22.2c6.8 1.1 13.8 1.7 20.9 1.7s14.1-.6 20.9-1.7l19.8 22.2zM464 400c-26.5 0-48-21.5-48-48s21.5-48 48-48s48 21.5 48 48s-21.5 48-48 48z"/></svg> Backend
      * the rules that link inputs and outputs
      * `server`: a **function**

---
# UI vs Server

## UI (Frontend) : 
  - what users will interact with (operation are done inside your web browser, so on your computer)
  - <svg aria-hidden="true" role="img" viewBox="0 0 384 512" style="height:1em;width:0.75em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M0 32l34.9 395.8L191.5 480l157.6-52.2L384 32H0zm308.2 127.9H124.4l4.1 49.4h175.6l-13.6 148.4-97.9 27v.3h-1.1l-98.7-27.3-6-75.8h47.7L138 320l53.5 14.5 53.7-14.5 6-62.2H84.3L71.5 112.2h241.1l-4.4 47.7z"/></svg> HTML, <svg aria-hidden="true" role="img" viewBox="0 0 512 512" style="height:1em;width:1em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M480 32l-64 368-223.3 80L0 400l19.6-94.8h82l-8 40.6L210 390.2l134.1-44.4 18.8-97.1H29.5l16-82h333.7l10.5-52.7H56.3l16.3-82H480z"/></svg> CSS, <svg aria-hidden="true" role="img" viewBox="0 0 448 512" style="height:1em;width:0.88em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M0 32v448h448V32H0zm243.8 349.4c0 43.6-25.6 63.5-62.9 63.5-33.7 0-53.2-17.4-63.2-38.5l34.3-20.7c6.6 11.7 12.6 21.6 27.1 21.6 13.8 0 22.6-5.4 22.6-26.5V237.7h42.1v143.7zm99.6 63.5c-39.1 0-64.4-18.6-76.7-43l34.3-19.8c9 14.7 20.8 25.6 41.5 25.6 17.4 0 28.6-8.7 28.6-20.8 0-14.4-11.4-19.5-30.7-28l-10.5-4.5c-30.4-12.9-50.5-29.2-50.5-63.5 0-31.6 24.1-55.6 61.6-55.6 26.8 0 46 9.3 59.8 33.7L368 290c-7.2-12.9-15-18-27.1-18-12.3 0-20.1 7.8-20.1 18 0 12.6 7.8 17.7 25.9 25.6l10.5 4.5c35.8 15.3 55.9 31 55.9 66.2 0 37.8-29.8 58.6-69.7 58.6z"/></svg> JavaScript 
  - via <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg> (partially or entirely)

## Server (Backend) : 
  - the operations done under the hood on a remote computer (a server).
  - basically <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg> (running on the remote computer)
  - other languages via <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg>

### <svg aria-hidden="true" role="img" viewBox="0 0 512 512" style="height:1em;width:1em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M256 32c14.2 0 27.3 7.5 34.5 19.8l216 368c7.3 12.4 7.3 27.7 .2 40.1S486.3 480 472 480H40c-14.3 0-27.6-7.7-34.7-20.1s-7-27.8 .2-40.1l216-368C228.7 39.5 241.8 32 256 32zm0 128c-13.3 0-24 10.7-24 24V296c0 13.3 10.7 24 24 24s24-10.7 24-24V184c0-13.3-10.7-24-24-24zm32 224c0-17.7-14.3-32-32-32s-32 14.3-32 32s14.3 32 32 32s32-14.3 32-32z"/></svg>  inspector will show you HTML, CSS and JavaScript, not <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg> code,
### <svg aria-hidden="true" role="img" viewBox="0 0 512 512" style="height:1em;width:1em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M256 32c14.2 0 27.3 7.5 34.5 19.8l216 368c7.3 12.4 7.3 27.7 .2 40.1S486.3 480 472 480H40c-14.3 0-27.6-7.7-34.7-20.1s-7-27.8 .2-40.1l216-368C228.7 39.5 241.8 32 256 32zm0 128c-13.3 0-24 10.7-24 24V296c0 13.3 10.7 24 24 24s24-10.7 24-24V184c0-13.3-10.7-24-24-24zm32 224c0-17.7-14.3-32-32-32s-32 14.3-32 32s14.3 32 32 32s32-14.3 32-32z"/></svg> when you are developing the app, the server is your computer!

---
# Shiny has its own ecosystem

### Not just one package!

### See https://shiny.rstudio.com/

### See RStudio's [Shiny apps gallery](https://shiny.rstudio.com/gallery/) for many examples.

### List of resources: [awesome-shiny-extensions](https://github.com/nanxstats/awesome-shiny-extensions)

---
# Shiny pros and cons

## Pros

- Use all <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg>'s capabilities (data analysis, visualization, etc.) in a Web application!

- Takes no time to build a simple (yet personalized) application.

- Applications can be run locally, deployed on R Studio's [Shiny Server](https://rstudio.com/products/shiny/shiny-server/), or to a hosting service such as [shinyapps.io](https://shinyapps.io), or your own server.

- Extensive documentation and material available for shiny applications.

- As often with <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg>, one of the major strength is the community: (academics / researchers)

--
  
- Growing bigger and bigger, getting better and better

---
# Shiny pros and cons

## Cons

- Syntax and logic of a Shiny application is a little bit different than what we are usually used to with <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg>.

- Takes some time to learn, require a more complex mental model.

- Harder to troubleshoot (at least when we start).

- Because it is more complex (another layer), it is worthwhile to really ponder whether a shiny application is necessary for what we wish to accomplish. _"Do you really need it?"_

---
# Shiny, an example <svg aria-hidden="true" role="img" viewBox="0 0 640 512" style="height:1em;width:1.25em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M64 96c0-35.3 28.7-64 64-64H512c35.3 0 64 28.7 64 64V352H512V96H128V352H64V96zM0 403.2C0 392.6 8.6 384 19.2 384H620.8c10.6 0 19.2 8.6 19.2 19.2c0 42.4-34.4 76.8-76.8 76.8H76.8C34.4 480 0 445.6 0 403.2zM281 209l-31 31 31 31c9.4 9.4 9.4 24.6 0 33.9s-24.6 9.4-33.9 0l-48-48c-9.4-9.4-9.4-24.6 0-33.9l48-48c9.4-9.4 24.6-9.4 33.9 0s9.4 24.6 0 33.9zM393 175l48 48c9.4 9.4 9.4 24.6 0 33.9l-48 48c-9.4 9.4-24.6 9.4-33.9 0s-9.4-24.6 0-33.9l31-31-31-31c-9.4-9.4-9.4-24.6 0-33.9s24.6-9.4 33.9 0z"/></svg>

## Spatial reporting tool

### **Bedford Institute of Oceanography, DFO**

* <svg aria-hidden="true" role="img" viewBox="0 0 496 512" style="height:1em;width:0.97em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M165.9 397.4c0 2-2.3 3.6-5.2 3.6-3.3.3-5.6-1.3-5.6-3.6 0-2 2.3-3.6 5.2-3.6 3-.3 5.6 1.3 5.6 3.6zm-31.1-4.5c-.7 2 1.3 4.3 4.3 4.9 2.6 1 5.6 0 6.2-2s-1.3-4.3-4.3-5.2c-2.6-.7-5.5.3-6.2 2.3zm44.2-1.7c-2.9.7-4.9 2.6-4.6 4.9.3 2 2.9 3.3 5.9 2.6 2.9-.7 4.9-2.6 4.6-4.6-.3-1.9-3-3.2-5.9-2.9zM244.8 8C106.1 8 0 113.3 0 252c0 110.9 69.8 205.8 169.5 239.2 12.8 2.3 17.3-5.6 17.3-12.1 0-6.2-.3-40.4-.3-61.4 0 0-70 15-84.7-29.8 0 0-11.4-29.1-27.8-36.6 0 0-22.9-15.7 1.6-15.4 0 0 24.9 2 38.6 25.8 21.9 38.6 58.6 27.5 72.9 20.9 2.3-16 8.8-27.1 16-33.7-55.9-6.2-112.3-14.3-112.3-110.5 0-27.5 7.6-41.3 23.6-58.9-2.6-6.5-11.1-33.3 2.6-67.9 20.9-6.5 69 27 69 27 20-5.6 41.5-8.5 62.8-8.5s42.8 2.9 62.8 8.5c0 0 48.1-33.6 69-27 13.7 34.7 5.2 61.4 2.6 67.9 16 17.7 25.8 31.5 25.8 58.9 0 96.5-58.9 104.2-114.8 110.5 9.2 7.9 17 22.9 17 46.4 0 33.7-.3 75.4-.3 83.6 0 6.5 4.6 14.4 17.3 12.1C428.2 457.8 496 362.9 496 252 496 113.3 383.5 8 244.8 8zM97.2 352.9c-1.3 1-1 3.3.7 5.2 1.6 1.6 3.9 2.3 5.2 1 1.3-1 1-3.3-.7-5.2-1.6-1.6-3.9-2.3-5.2-1zm-10.8-8.1c-.7 1.3.3 2.9 2.3 3.9 1.6 1 3.6.7 4.3-.7.7-1.3-.3-2.9-2.3-3.9-2-.6-3.6-.3-4.3.7zm32.4 35.6c-1.6 1.3-1 4.3 1.3 6.2 2.3 2.3 5.2 2.6 6.5 1 1.3-1.3.7-4.3-1.3-6.2-2.2-2.3-5.2-2.6-6.5-1zm-11.4-14.7c-1.6 1-1.6 3.6 0 5.9 1.6 2.3 4.3 3.3 5.6 2.3 1.6-1.3 1.6-3.9 0-6.2-1.4-2.3-4-3.3-5.6-2z"/></svg> https://github.com/inSilecoInc/shinySpatialApp_origin

---
class: inverse, center, middle

![:custom_hr]()

---
# Reactive programming

## Why?

* When I change `Number of obs` to `n` then :
  - `n` new values are drawn,
  - a new histogram is generated and displayed
--

* **reactivity**!
    - **reactive programming** = **event-driven programming** the event is "data has changed" (think "spreadsheet")
    - see [this answer on <svg aria-hidden="true" role="img" viewBox="0 0 384 512" style="height:1em;width:0.75em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M290.7 311L95 269.7 86.8 309l195.7 41zm51-87L188.2 95.7l-25.5 30.8 153.5 128.3zm-31.2 39.7L129.2 179l-16.7 36.5L293.7 300zM262 32l-32 24 119.3 160.3 32-24zm20.5 328h-200v39.7h200zm39.7 80H42.7V320h-40v160h359.5V320h-40z"/></svg>](https://stackoverflow.com/questions/34495117/how-is-reactive-programming-different-than-event-driven-programming),

---
# Reactive programming

- That's the tricky part! As <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg> users we do not use **reactive programming**.

- we are familiar with different paradigms:
  - **imperative programming**: "do this"
  - **functional programming**: we create and call functions
  - **array programming**: we apply operations on vectors
  - ...

- ... but not **reactive programming** that is more **declarative**: "make sure that this is done"

---
# Reactive programming

## Making lemonade...

- with **imperative programming**: 
> "pour 1 L of cold water, stir in 30 mL of lemon juice and add 1 tablespoon of map syrup"

- with **declarative programming**:
> "you have 1 L of cold water, 30 mL of lemon juice and 1 tablespoon of map syrup, make me a lemonade"

---
# Reactive programming

## So

- **reactive programming** = **event-driven programming** the event is "data changed"

- **reactive programming** is more declarative

- **reactive programming** is not specific to Shiny (e.g. https://quarto.org/docs/computations/ojs.html)

---
# Reactive programming

```r
a <- 2
b <- 2 * a
cat("a =", a, " | ", "b =", b)
#> a = 2  |  b = 4
```

Would `b` change if `a` changes?

```r
a <- 3
cat("a =", a, " | ", "b =", b)
#> a = 3  |  b = 4
```

Nope!

???
DO NOT BE SHY AND ASK US WHAT IS THAT PIECE OF CODE

---
# Reactive programming

```r
# shiny must be installed
library(shiny)
reactiveConsole(TRUE)
```

```r
a <- reactiveVal(2)
b <- reactive({2 * a()})
cat("a =", a(), " | ", "b =", b())
#> a = 2  |  b = 4
```

Would `b` change if `a` changes?

```r
a(3)
cat("a =", a(), " | ", "b =", b())
#> a = 3  |  b = 6
```

Yes! Because now variables are somehow linked!

---
# Reactive programming .font80[&nbsp; <svg aria-hidden="true" role="img" viewBox="0 0 448 512" style="height:1em;width:0.88em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M438.6 278.6c12.5-12.5 12.5-32.8 0-45.3l-160-160c-12.5-12.5-32.8-12.5-45.3 0s-12.5 32.8 0 45.3L338.8 224 32 224c-17.7 0-32 14.3-32 32s14.3 32 32 32l306.7 0L233.4 393.4c-12.5 12.5-12.5 32.8 0 45.3s32.8 12.5 45.3 0l160-160z"/></svg> building blocks]

.pull-left[
  ## 1. reactive values
]
.pull-right[
  ![:scale 26%](img/reactive_graphs/reactVal.png)
]

* starting points, no reactivity without them!
* could be any <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg> objects
* two ways to initiate them: `reactiveVal()` and `reactiveValues()`

.pull-left[
  ## 1. reactive values
]
.pull-right[
  ![:scale 26%](img/reactive_graphs/reactVal.png)
]

```r
a <- reactiveVal(2)
a()
#> [1] 2
x <- reactiveVal(list(a = 1, mydf = data.frame(a = c(1, 2), b = letters[1:2])))
x()
#> $a
#> [1] 1
#> 
#> $mydf
#>   a b
#> 1 1 a
#> 2 2 b
```

.pull-left[
  ## 1. reactive values
]
.pull-right[
  ![:scale 26%](img/reactive_graphs/reactVal.png)
]

```r
a <- reactiveValues(a = 1, mydf = data.frame(a = c(1, 2), b = letters[1:2]))
a
#> <ReactiveValues> 
#>   Values:    a, mydf 
#>   Readonly:  FALSE
a$a
#> [1] 1
a$mydf
#>   a b
#> 1 1 a
#> 2 2 b
```

???
no parentheses

.pull-left[
  ## 2. reactive expressions
]
.pull-right[
  ![:scale 30%](img/reactive_graphs/reactExp.png)
]

* depends on reactive values or other reactive expressions
* can be used in another reactive expression
* special functions (lazy and cached) 
* intermediate entities
* can be used to avoid duplication in your reactive code

.pull-left[
  ## 2. reactive expressions
]
.pull-right[
  ![:scale 30%](img/reactive_graphs/reactExp.png)
]

```r
a <- reactiveVal(2)
a()
#> [1] 2
b <- reactive({2*a()})
b()
#> [1] 4
```
--

```r
a(4)
b()
#> [1] 8
```

.pull-left[
  ## 2. reactive expressions
]
.pull-right[
  ![:scale 30%](img/reactive_graphs/reactExp.png)
]

```r
a <- reactiveVal(2)
b <- reactive({2 * a()})
a2 <- reactiveVal(runif(1))
# I avoid using `c` as name variable purposely
d <- reactive({
  print("executing reactive")
  b() + a2()
}) 
d()
#> [1] "executing reactive"
#> [1] 4.644578
a(3)
d()
#> [1] "executing reactive"
#> [1] 6.644578
```

???
I have to call `d()`, so not automatically!
missing something that would watch change in a or a2!
use runif(1) instead of 2 --> exercice?

.pull-left[
  ## 3. Observers
]
.pull-right[
  ![:scale 25%](img/reactive_graphs/reactObs.png)
]

* can read reactive values and call reactive expressions
* will automatically re-execute when those dependencies change
* eager (“infectious" eagerness) and forgetful
* the value returned by an observer is ignored

<br>

.center[![:scale 32%](img/reactive_graphs/simpleGraph0.png)]

.center[![:scale 60%](img/reactive_graphs/simpleGraph.png)]

.pull-left[
  ## 3. Observers
]
.pull-right[
  ![:scale 25%](img/reactive_graphs/reactObs.png)
]

```r
observe(d())
a(1)
a(2)
a2(1)
```

???
You won't use observe()
to do in console

### 1. Reactive values ~ "*special variables*""

### 2. Reactive expressions ~ "*special functions*""

### 3. Observers ~ "*special what?*"

???
r <- observe(d())
r$.label
r$.func() 
r$.func <- function(){d() + 1}

---
# Exercise

* Fahrenheit to Celsius
  * hints: 
    - make `temp` your reactive variable that have the temperature in Fahrenheit
    - 1`C` = (1`F` - 32) * 5/9 (https://en.wikipedia.org/wiki/Fahrenheit)

* feet to meters

* Fahrenheit to Celsius and vice-versa

* [How to measure things like a Canadian](https://preview.redd.it/k1brffgbngk31.png?width=681&format=png&auto=webp&s=8cc428c345b687a3f79d8e481561781f38d0630e)

---
# <svg aria-hidden="true" role="img" viewBox="0 0 512 512" style="height:1em;width:1em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M256 32c14.2 0 27.3 7.5 34.5 19.8l216 368c7.3 12.4 7.3 27.7 .2 40.1S486.3 480 472 480H40c-14.3 0-27.6-7.7-34.7-20.1s-7-27.8 .2-40.1l216-368C228.7 39.5 241.8 32 256 32zm0 128c-13.3 0-24 10.7-24 24V296c0 13.3 10.7 24 24 24s24-10.7 24-24V184c0-13.3-10.7-24-24-24zm32 224c0-17.7-14.3-32-32-32s-32 14.3-32 32s14.3 32 32 32s32-14.3 32-32z"/></svg> Special cases

### Special cases that we use all the time to let Shiny do its magic!

#### - **`input`**: read-only **reactive values**

#### - **`output`**: special **observers**

<br>

### **`input`** <svg aria-hidden="true" role="img" viewBox="0 0 448 512" style="height:1em;width:0.88em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M438.6 278.6c12.5-12.5 12.5-32.8 0-45.3l-160-160c-12.5-12.5-32.8-12.5-45.3 0s-12.5 32.8 0 45.3L338.8 224 32 224c-17.7 0-32 14.3-32 32s14.3 32 32 32l306.7 0L233.4 393.4c-12.5 12.5-12.5 32.8 0 45.3s32.8 12.5 45.3 0l160-160z"/></svg> **`output`**

.center[![:scale 40%](img/reactive_graphs/simpleGraph0.png)]

--
 
### **`input`** <svg aria-hidden="true" role="img" viewBox="0 0 448 512" style="height:1em;width:0.88em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M438.6 278.6c12.5-12.5 12.5-32.8 0-45.3l-160-160c-12.5-12.5-32.8-12.5-45.3 0s-12.5 32.8 0 45.3L338.8 224 32 224c-17.7 0-32 14.3-32 32s14.3 32 32 32l306.7 0L233.4 393.4c-12.5 12.5-12.5 32.8 0 45.3s32.8 12.5 45.3 0l160-160z"/></svg> **`reactive expression`** <svg aria-hidden="true" role="img" viewBox="0 0 448 512" style="height:1em;width:0.88em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M438.6 278.6c12.5-12.5 12.5-32.8 0-45.3l-160-160c-12.5-12.5-32.8-12.5-45.3 0s-12.5 32.8 0 45.3L338.8 224 32 224c-17.7 0-32 14.3-32 32s14.3 32 32 32l306.7 0L233.4 393.4c-12.5 12.5-12.5 32.8 0 45.3s32.8 12.5 45.3 0l160-160z"/></svg> **`output`**

.center[![:scale 70%](img/reactive_graphs/simpleGraph.png)]

---
# Study case

```R
# Define the UI
ui <- bootstrapPage(
  numericInput('n', 'Number of obs', n),
  plotOutput('plot')
)
```

---
# Study case

```R
# Define the server code
server <- function(input, output) {
  output$plot <- renderPlot({
    hist(runif(input$n))
  })
}
```

* `input$n`: reactive value `n`
* `ouput$plot`: observer `plot`

### Reactive graph:  **`input$n`** <svg aria-hidden="true" role="img" viewBox="0 0 448 512" style="height:1em;width:0.88em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M438.6 278.6c12.5-12.5 12.5-32.8 0-45.3l-160-160c-12.5-12.5-32.8-12.5-45.3 0s-12.5 32.8 0 45.3L338.8 224 32 224c-17.7 0-32 14.3-32 32s14.3 32 32 32l306.7 0L233.4 393.4c-12.5 12.5-12.5 32.8 0 45.3s32.8 12.5 45.3 0l160-160z"/></svg> **`output$plot`**

.center[![:scale 40%](img/reactive_graphs/simpleGraph0.png)]

???
Shiny is gonna take care of it for you

---
# Reactive graph

.center[![:scale 40%](img/reactive_graphs/simpleGraph0.png)]

### with [`Shiny`](https://CRAN.R-project.org/package=Shiny) we build a **reactive graph** and Shiny takes care of it for us!

### In a reactive graph, there are "variables" that depend on each other and this is what enables the interactivity!

---
# Building a shiny app

### Building a more complex graph!

.center[![:scale 75%](img/reactive_graphs/complexGraph.png)]

* `reactiveVal`, `oberveEvent`, `isolate()`, etc.

---
# Let's sum up

1. Shiny allows you to create web applications with <svg aria-hidden="true" role="img" viewBox="0 0 581 512" style="height:1em;width:1.13em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M581 226.6C581 119.1 450.9 32 290.5 32S0 119.1 0 226.6C0 322.4 103.3 402 239.4 418.1V480h99.1v-61.5c24.3-2.7 47.6-7.4 69.4-13.9L448 480h112l-67.4-113.7c54.5-35.4 88.4-84.9 88.4-139.7zm-466.8 14.5c0-73.5 98.9-133 220.8-133s211.9 40.7 211.9 133c0 50.1-26.5 85-70.3 106.4-2.4-1.6-4.7-2.9-6.4-3.7-10.2-5.2-27.8-10.5-27.8-10.5s86.6-6.4 86.6-92.7-90.6-87.9-90.6-87.9h-199V361c-74.1-21.5-125.2-67.1-125.2-119.9zm225.1 38.3v-55.6c57.8 0 87.8-6.8 87.8 27.3 0 36.5-38.2 28.3-87.8 28.3zm-.9 72.5H365c10.8 0 18.9 11.7 24 19.2-16.1 1.9-33 2.8-50.6 2.9v-22.1z"/></svg>

2. A shiny app includes a user interface (`ui`) and a server function (`server`)

3. A shiny app uses reactive programming to generate outputs based on users inputs

4. Shiny takes care of the reactive graph you built: inputs and outputs are presented in `ui`, the rules that link them are defined in `server`

---
# Let's practice

### <svg aria-hidden="true" role="img" viewBox="0 0 640 512" style="height:1em;width:1.25em;vertical-align:-0.125em;margin-left:auto;margin-right:auto;font-size:inherit;fill:currentColor;overflow:visible;position:relative;"><path d="M64 96c0-35.3 28.7-64 64-64H512c35.3 0 64 28.7 64 64V352H512V96H128V352H64V96zM0 403.2C0 392.6 8.6 384 19.2 384H620.8c10.6 0 19.2 8.6 19.2 19.2c0 42.4-34.4 76.8-76.8 76.8H76.8C34.4 480 0 445.6 0 403.2zM281 209l-31 31 31 31c9.4 9.4 9.4 24.6 0 33.9s-24.6 9.4-33.9 0l-48-48c-9.4-9.4-9.4-24.6 0-33.9l48-48c9.4-9.4 24.6-9.4 33.9 0s9.4 24.6 0 33.9zM393 175l48 48c9.4 9.4 9.4 24.6 0 33.9l-48 48c-9.4 9.4-24.6 9.4-33.9 0s-9.4-24.6 0-33.9l31-31-31-31c-9.4-9.4-9.4-24.6 0-33.9s24.6-9.4 33.9 0z"/></svg> Create the reactive graph of this application [Iris k-means clustering](https://shiny.rstudio.com/gallery/kmeans-example.html)

<br>

.pull-left[
```R
a <- reactiveVal(2)
b <- reactive({2 * a()})
a2 <- reactiveVal(runif(1))
d <- reactive({
  print("executing reactive")
  b() + a2()
}) 
observe(d())
```
]
.pull-right[
```R
a <- reactiveVal(2)
b <- reactive({2 * a()})
d <- reactive({
  print("executing reactive")
  b() + runif(1)
}) 
observe(d())
```
]