shiny/_includes/tutorial/inputs-and-outputs.md

Inputs & Outputs

Accepting Input

ui.R

library(shiny)

# Define UI for miles per gallon application
shinyUI(pageWithSidebar(

  # Application title
  headerPanel("Miles Per Gallon"),

  # Sidebar with controls to select the variable to plot against mpg
  # and to specify whether outliers should be included
  sidebarPanel(
    selectInput("variable", "Variable:",
                list("Cylinders" = "cyl", 
                     "Transmission" = "am", 
                     "Gears" = "gear")),

    checkboxInput("outliers", "Show outliers", FALSE)
  ),

  mainPanel()
))

Showing Output

server.R

library(shiny)
library(datasets)

# We tweak the "am" field to have nicer factor labels. Since this doesn't
# rely on any user inputs we can do this once at startup and then use the
# value throughout the lifetime of the application
mpgData <- mtcars
mpgData$am <- factor(mpgData$am, labels = c("Automatic", "Manual"))


# Define server logic required to plot various variables against mpg
shinyServer(function(input, output) {

  # Compute the forumla text in a reactive function since it is 
  # shared by the output$caption and output$mpgPlot functions
  formulaText <- reactive(function() {
    paste("mpg ~", input$variable)
  })

  # Return the formula text for printing as a caption
  output$caption <- reactiveText(function() {
    formulaText()
  })

  # Generate a plot of the requested variable against mpg and only 
  # include outliers if requested
  output$mpgPlot <- reactivePlot(function() {
    boxplot(as.formula(formulaText()), 
            data = mpgData,
            outline = input$outliers)
  })
})

ui.R

library(shiny)

# Define UI for miles per gallon application
shinyUI(pageWithSidebar(

  # Application title
  headerPanel("Miles Per Gallon"),

  # Sidebar with controls to select the variable to plot against mpg
  # and to specify whether outliers should be included
  sidebarPanel(
    selectInput("variable", "Variable:",
                list("Cylinders" = "cyl", 
                     "Transmission" = "am", 
                     "Gears" = "gear")),

    checkboxInput("outliers", "Show outliers", FALSE)
  ),

  # Show the caption and plot of the requested variable against mpg
  mainPanel(
    h3(textOutput("caption")),

    plotOutput("mpgPlot")
  )
))