Week 11: Shiny, Part III

Robert W. Walker

Overview

Overview

1. AMA
2. Tidy evaluation again
3. Shiny, Part III
4. Best Practices

The Assignment [Multi-week]

A shiny

Syllabus Module for Week 11

A Handy Styling Tool

Link to discord

Another Handy Docker Tool

Link to discord

AMA

Tidy evaluation

Environments and data.

tidy evaluation

The Path Forward

next time

Fun with docker

We will walk through at least one example as time permits.

Docker in brief

• docker build
• docker push
• The Cloud Run Console

This can be tricky with M1 macs as some images do not play nicely. NB: I am just beginning to explore this because it did not occur to me that it would be an issue from my Intel workstation.

Shiny Part III

Working through these chapters

Start with:

library(shiny)
library(dplyr)
ui <- ...
server <- ...
shinyApp(ui, server)

and the steps will fill in a ui and server

Chapter 12

• tidy evaluation

Screen shot

Passing variable names

library(shiny)
library(dplyr)
ui <- fluidPage(
  selectInput("var", "Sort by", choices = names(mtcars)),
  checkboxInput("desc", "Descending order?"),
  tableOutput("data")
)
server <- function(input, output, session) {
  sorted <- reactive({
    if (input$desc) {
      arrange(mtcars, desc(.data[[input$var]]))
    } else {
      arrange(mtcars, .data[[input$var]])
    }
  })
  output$data <- renderTable(sorted())
}
shinyApp(ui, server)

The importance of req. What does it do?

Shot of help

Chapter 13

Why reactivity?

Shot

Playing with Reactive

Simple Example

Excel is Reactive, That’s Why It is Popular

It started with VisiCalc…

The History

Chapter 14

The reactive graph is worth playing with. Due to modern defaults in RStudio, the workflow is a bit tricky. We will have to run the app in the console.

Settings

shinylog

Run it and close it to get this.

reactlog

Chapter 15

Reactives, single and plural

Two types

They Behave a bit Differently

Behavior is a bit different

Observing

Pay very close attention to 15.3 on observe versus observeEvent. The example in 16.3.3…

library(shiny)
reactiveConsole(TRUE)
x <- reactiveVal(1)
y <- observe({
  x()
  observe(print(x()))
})
x(2)
x(3)
x(2)

On Isolate

Details

Isolate is not all that common because the behavior is embedded in two common tools:

observeEvent and eventReactive

15.5 on timing

part 1 - invalidateLater

Polling

part 2 - Details

on.exit()

15.5.2 and the importance of timing. Using on.exit

Chapter 16: Escaping the Graph

Video

The Case Studies

Part 1

Part 2

Two that are related.

Part 3

Part 4

The timer

Timer

Warnings:

It is quite easy to get carried away and muddle the flow.

Anti-patterns

The Path Forward

Shot of Final Section

The Overview

Best Practices