Example: A Shiny Application

This example demonstrates how to create and run a Shiny application and view the associated UI while in an active session.

Create a new project and run an R console.

Create the files, ui.R and server.R in the project, and copy the content of the following example files provided by Shiny by RStudio:

# ui.R

library(shiny)

# Define UI for application that draws a histogram
shinyUI(fluidPage(

  # Application title
  titlePanel("Hello Shiny!"),

  # Sidebar with a slider input for the number of bins
  sidebarLayout(
    sidebarPanel(
      sliderInput("bins",
                  "Number of bins:",
                  min = 1,
                  max = 50,
                  value = 30)
    ),

    # Show a plot of the generated distribution
    mainPanel(
      plotOutput("distPlot")
    )
  )
))

# server.R 

library(shiny)

# Define server logic required to draw a histogram
shinyServer(function(input, output) {

  # Expression that generates a histogram. The expression is
  # wrapped in a call to renderPlot to indicate that:
  #
  #  1) It is "reactive" and therefore should re-execute automatically
  #     when inputs change
  #  2) Its output type is a plot

  output$distPlot <- renderPlot({
    x    <- faithful[, 2]  # Old Faithful Geyser data
    bins <- seq(min(x), max(x), length.out = input$bins + 1)

    # draw the histogram with the specified number of bins
    hist(x, breaks = bins, col = 'darkgray', border = 'white')
  })
})

Run the following code in the interactive workbench prompt to install the Shiny package, load the library into the engine, and run the Shiny application.
R
```
install.packages('shiny') 

library('shiny')

runApp(port=as.numeric(Sys.getenv("CDSW_READONLY_PORT")), host="127.0.0.1", launch.browser="FALSE")
```
Access the web application.
- Click the grid icon in the upper right hand corner of the Cloudera AI web application, and select the Shiny UI, Hello Shiny!, from the dropdown menu.
- Access the web application directly by visiting the URL:
  https://public-[session-id].[CML host]/

The UI will be active as long as the session is still running.