Reactive flow Building Web Applications in R with Shiny - - PowerPoint PPT Presentation

▶
reactive flow
SMART_READER_LITE
LIVE PREVIEW

Reactive flow Building Web Applications in R with Shiny - - PowerPoint PPT Presentation

Mar 01, 2023 15 likes •466 views

BUILDING WEB APPLICATIONS IN R WITH SHINY Reactive flow Building Web Applications in R with Shiny Reactivity, in spreadsheets Building Web Applications in R with Shiny Reactivity, in spreadsheets Building Web Applications in R with Shiny

slide-1
SLIDE 1

BUILDING WEB APPLICATIONS IN R WITH SHINY

Reactive flow

slide-2
SLIDE 2

Building Web Applications in R with Shiny

Reactivity, in spreadsheets

slide-3
SLIDE 3

Building Web Applications in R with Shiny

Reactivity, in spreadsheets

slide-4
SLIDE 4

Building Web Applications in R with Shiny

Reactivity, in spreadsheets

slide-5
SLIDE 5

Building Web Applications in R with Shiny

Reactivity, in spreadsheets

slide-6
SLIDE 6

Building Web Applications in R with Shiny

Reactivity, in spreadsheets

slide-7
SLIDE 7

Building Web Applications in R with Shiny

# Set alpha level sliderInput(inputId = "alpha", label = "Alpha:", min = 0, max = 1, value = 0.5)

Reactions

The input$ list stores the current value of each input

  • bject under its name.

input$alpha

input$alpha = 0.2 input$alpha = 0.5 input$alpha = 0.8

slide-8
SLIDE 8

Building Web Applications in R with Shiny

Reactivity 101

Reactivity automatically occurs when an input value is used to render an output object.

# Define server function required to create the scatterplot server <- function(input, output) { # Create the scatterplot object the plotOutput function is expecting

  • utput$scatterplot <- renderPlot({

ggplot(data = movies, aes_string(x = input$x, y = input$y)) + geom_point(alpha = input$alpha) }) }

slide-9
SLIDE 9

Building Web Applications in R with Shiny

input$x

  • utput$y

expression()

Schedule updates invalidateLater()

run(this)

Trigger arbitrary code

  • bserveEvent()
  • bserve()

Create your

  • wn reactive values

reactiveValues() reactiveFileReader() reactivePoll() *Input()

Update

Delay reactions eventReactive() Modularize reactions reactive() Prevent reactions isolate() Render reactive output render*()

Reactive flow

slide-10
SLIDE 10

Building Web Applications in R with Shiny

Reactive flow, simplified

input$x

  • utput$y

expression() Update

Render reactive output render*() Create your

  • wn reactive values

*Input()

slide-11
SLIDE 11

BUILDING WEB APPLICATIONS IN R WITH SHINY

Let's practice!

slide-12
SLIDE 12

BUILDING WEB APPLICATIONS IN R WITH SHINY

UI inputs

slide-13
SLIDE 13

Building Web Applications in R with Shiny

slide-14
SLIDE 14

Building Web Applications in R with Shiny

slide-15
SLIDE 15

Building Web Applications in R with Shiny

checkboxInput

Add a checkbox input to specify whether the data plotted should be shown in a data table.

  • 1. ui: Add an input widget that the user can interact with

to check/uncheck the box.

  • 2. ui: Add an output defining where the data table should

appear.

  • 3. server: Add a reactive expression that creates the

data table if the checkbox is checked.

slide-16
SLIDE 16

Building Web Applications in R with Shiny

checkboxInput

Add a checkbox input to specify whether the data plotted should be shown in a data table.

  • 1. ui: Add an input widget that the user can interact with

to check/uncheck the box.

# Show data table checkboxInput(inputId = "show_data", label = "Show data table", value = TRUE)

slide-17
SLIDE 17

Building Web Applications in R with Shiny

Watch for commas!

sidebarPanel( # Select variable for y-axis selectInput(inputId = "y", label = "Y-axis:", choices = c("imdb_rating", "imdb_num_votes", "critics_score", "audience_score", "runtime"), selected = "audience_score"), # Select variable for x-axis selectInput(inputId = "x", label = "X-axis:", choices = c("imdb_rating", "imdb_num_votes", "critics_score", "audience_score", "runtime"), selected = "critics_score"), # Show data table checkboxInput(inputId = "show_data", label = "Show data table", value = TRUE) )

slide-18
SLIDE 18

Building Web Applications in R with Shiny

checkboxInput

Add a checkbox input to specify whether the data plotted should be shown in a data table.

mainPanel( # Show scatterplot plotOutput(outputId = "scatterplot"), # Show data table DT::dataTableOutput(outputId = "moviestable") )

  • 2. ui: Add an output to the UI defining where the data

table should appear.

slide-19
SLIDE 19

Building Web Applications in R with Shiny

checkboxInput

Add a checkbox input to specify whether the data plotted should be shown in a data table.

# Print data table if checked

  • utput$moviestable <- DT::renderDataTable({

if(input$show_data){ DT::datatable(data = movies %>% select(1:7),

  • ptions = list(pageLength = 10),

rownames = FALSE) } })

  • 3. server: Add a reactive expression that creates the

data table if the checkbox is checked.

slide-20
SLIDE 20

Building Web Applications in R with Shiny

slide-21
SLIDE 21

Building Web Applications in R with Shiny

slide-22
SLIDE 22

Building Web Applications in R with Shiny

Scoping

  • We saw that the data loaded on top of the Shiny app

is visible to the server.

  • It is also visible to the UI.

# Display number of observations HTML(paste0("The dataset has ", nrow(movies), “observations."))

slide-23
SLIDE 23

BUILDING WEB APPLICATIONS IN R WITH SHINY

Let's practice!

slide-24
SLIDE 24

BUILDING WEB APPLICATIONS IN R WITH SHINY

Rendering functions

slide-25
SLIDE 25

Building Web Applications in R with Shiny

works with

slide-26
SLIDE 26

Building Web Applications in R with Shiny

works with

slide-27
SLIDE 27

Building Web Applications in R with Shiny

slide-28
SLIDE 28

Building Web Applications in R with Shiny

slide-29
SLIDE 29

Building Web Applications in R with Shiny

renderTable

Add a table beneath the plot displaying summary statistics for a new variable: score_ratio = audience_score / critics_score.

  • 1. Calculate the new variable.
  • 2. ui: Add an input widget that the user can interact with to

check boxes for selected title types.

  • 3. ui: Add an output defining where the summary table should

appear.

  • 4. server: Add a reactive expression that creates the summary

table.

slide-30
SLIDE 30

Building Web Applications in R with Shiny

renderTable

Add a table beneath the plot displaying summary statistics for a new variable: score_ratio = audience_score / critics_score.

  • 1. Calculate the new variable.

# Create new variable: # ratio of critics and audience scores movies <- movies %>% mutate(score_ratio = audience_score / critics_score)

slide-31
SLIDE 31

Building Web Applications in R with Shiny

renderTable

Add a table beneath the plot displaying summary statistics for a new variable: score_ratio = audience_score / critics_score.

  • 2. ui: Add an input widget that the user can interact with to

check boxes for selected title types.

# Subset for title types checkboxGroupInput(inputId = "selected_title_type", label = "Select title type:", choices = levels(movies$title_type), selected = levels(movies$title_type))

slide-32
SLIDE 32

Building Web Applications in R with Shiny

renderTable

Add a table beneath the plot displaying summary statistics for a new variable: score_ratio = audience_score / critics_score.

  • 3. ui: Add an output defining where the summary table should

appear.

mainPanel( # Show scatterplot plotOutput(outputId = "scatterplot"), # Show data table tableOutput(outputId = "summarytable") )

slide-33
SLIDE 33

Building Web Applications in R with Shiny

renderTable

Add a table beneath the plot displaying summary statistics for a new variable: score_ratio = audience_score / critics_score.

  • 4. server: Add a reactive expression that creates the summary

table.

  • utput$summarytable <- renderTable(

{movies %>% filter(title_type %in% input$selected_title_type) %>% group_by(mpaa_rating) %>% summarise(Mean = mean(score_ratio), SD = sd(score_ratio), n = n())}, striped = TRUE, spacing = "l", align = "lccr", digits = 4, width = "90%", caption = "Score ratio (audience / critics' scores) summary statistics by MPAA rating." )

slide-34
SLIDE 34

Building Web Applications in R with Shiny

slide-35
SLIDE 35

Building Web Applications in R with Shiny

renderTable

Add a table beneath the plot displaying summary statistics for a new variable: score_ratio = audience_score / critics_score.

  • 4. server: Add a reactive expression that creates the summary

table.

  • utput$summarytable <- renderTable(

{movies %>% filter(title_type %in% input$selected_title_type) %>% group_by(mpaa_rating) %>% summarise(Mean = mean(score_ratio), SD = sd(score_ratio), n = n())}, striped = TRUE, spacing = "l", align = "lccr", digits = 4, width = "90%", caption = "Score ratio (audience / critics' scores) summary statistics by MPAA rating." )

slide-36
SLIDE 36

Building Web Applications in R with Shiny

Recap

  • Shiny has a variety of render* functions with

corresponding *Output functions to create and display outputs.

  • render* functions can take on multiple arguments,

the first being the expression for the desired output.

  • The expression in the render* function should be

wrapped in curly braces.

slide-37
SLIDE 37

BUILDING WEB APPLICATIONS IN R WITH SHINY

Let's practice!

slide-38
SLIDE 38

BUILDING WEB APPLICATIONS IN R WITH SHINY

UI outputs

slide-39
SLIDE 39

Building Web Applications in R with Shiny

slide-40
SLIDE 40

Building Web Applications in R with Shiny

slide-41
SLIDE 41

Building Web Applications in R with Shiny

plotOutput

Select points on the plot via brushing, and report the selected points in a data table underneath the plot.

  • 1. ui: Add functionality to plotOutput to select points

via brushing.

  • 2. ui: Add an output defining where the data table should

appear.

  • 3. server: Add a reactive expression that creates the

data table for the selected points.

slide-42
SLIDE 42

Building Web Applications in R with Shiny

plotOutput

Select points on the plot via brushing, and report the selected points in a data table underneath the plot.

  • 1. ui: Add functionality to plotOutput to select points

via brushing.

# Show scatterplot with brushing capability plotOutput(outputId = "scatterplot", brush = "plot_brush")

slide-43
SLIDE 43

Building Web Applications in R with Shiny

plotOutput

Select points on the plot via brushing, and report the selected points in a data table underneath the plot.

  • 2. ui: Add an output defining where the data table should

appear.

# Show data table DT::dataTableOutput(outputId = "moviestable")

slide-44
SLIDE 44

Building Web Applications in R with Shiny

plotOutput

Select points on the plot via brushing, and report the selected points in a data table underneath the plot.

  • 3. server: Add a reactive expression that creates the

data table for the selected points.

# Print data table

  • utput$moviestable <- DT::renderDataTable({

brushedPoints(movies, input$plot_brush) %>% select(title, audience_score, critics_score) })

slide-45
SLIDE 45

BUILDING WEB APPLICATIONS IN R WITH SHINY

Let's practice!