shiny/_includes/tutorial/more-widgets.md

The More Widgets application demonstrates the help text and submit button widgets as well as the use of embedded HTML elements to customize formatting. To run the example type:

> library(shiny)
> runExample("07_widgets")

UI Enhancements

In this example we update the Shiny Text application with some additional controls and formatting, specifically:

• We added a helpText control to provide additional clarifying text alongside our input controls.
• We added a submitButton control to indicate that we don't want a live connection between inputs and outputs, but rather to wait until the user clicks that button to update the output. This is especially useful if computing output is computationally expensive.
• We added h4 elements (heading level 4) into the output pane. Shiny offers a variety of functions for including HTML elements directly in pages including headings, paragraphics, links, and more.

Here is the updated source code for the user-interface:

ui.R

library(shiny)

# Define UI for dataset viewer application
shinyUI(pageWithSidebar(

  # Application title.
  headerPanel("More Widgets"),

  # Sidebar with controls to select a dataset and specify the number
  # of observations to view. The helpText function is also used to 
  # include clarifying text. Most notably, the inclusion of a 
  # submitButton defers the rendering of output until the user 
  # explicitly clicks the button (rather than doing it immediately
  # when inputs change). This is useful if the computations required
  # to render output are inordinately time-consuming.
  sidebarPanel(
    selectInput("dataset", "Choose a dataset:", 
                choices = c("rock", "pressure", "cars")),

    numericInput("obs", "Number of observations to view:", 10),

    helpText("Note: while the data view will show only the specified",
             "number of observations, the summary will still be based",
             "on the full dataset."),

    submitButton("Update View")
  ),

  # Show a summary of the dataset and an HTML table with the requested
  # number of observations. Note the use of the h4 function to provide
  # an additional header above each output section.
  mainPanel(
    h4("Summary"),
    verbatimTextOutput("summary"),

    h4("Observations"),
    tableOutput("view")
  )
))

Server Script

All of the changes from the original Shiny Text application were to the user-interface, the server script remains the same:

server.R

library(shiny)
library(datasets)

# Define server logic required to summarize and view the selected dataset
shinyServer(function(input, output) {

  # Return the requested dataset
  datasetInput <- reactive(function() {
    switch(input$dataset,
           "rock" = rock,
           "pressure" = pressure,
           "cars" = cars)
  })

  # Generate a summary of the dataset
  output$summary <- reactivePrint(function() {
    dataset <- datasetInput()
    summary(dataset)
  })

  # Show the first "n" observations
  output$view <- reactiveTable(function() {
    head(datasetInput(), n = input$obs)
  })
})