# Shiny

# Create an app

Shiny is an R package developed by RStudio that allows the creation of web pages to interactively display the results of an analysis in R.

There are two simple ways to create a Shiny app:

  • in one .R file, or
  • in two files: ui.R and server.R.

A Shiny app is divided into two parts:

  • **ui**: A user interface script, controlling the layout and appearance of the application.
  • - **server**: A server script which contains code to allow the application to react.

    # One file

    library(shiny)
    
    # Create the UI
    ui <- shinyUI(fluidPage(
        # Application title
        titlePanel("Hello World!")
    ))
    
    # Create the server function
    server <- shinyServer(function(input, output){})
    
    # Run the app
    shinyApp(ui = ui, server = server)
    
    

    # Two files

    # Create ui.R file

    library(shiny)
    
    # Define UI for application
    shinyUI(fluidPage(  
      # Application title
      titlePanel("Hello World!")
    ))
    
    

    # Create server.R file

    library(shiny)
    
    # Define server logic
    shinyServer(function(input, output){})
    
    

    # Checkbox Group

    Create a group of checkboxes that can be used to toggle multiple choices independently. The server will receive the input as a character vector of the selected values.

    library(shiny)
    
    ui <- fluidPage(    
      checkboxGroupInput("checkGroup1", label = h3("This is a Checkbox group"), 
                     choices = list("1" = 1, "2" = 2, "3" = 3),
                     selected = 1),
      fluidRow(column(3, verbatimTextOutput("text_choice")))
      ) 
    
    
    server <- function(input, output){
      output$text_choice <- renderPrint({
        return(paste0("You have chosen the choice ",input$checkGroup1))})
    } 
    
    shinyApp(ui = ui, server = server)
    
    

    enter image description here

    It's possible to change the settings :

    • label : title
    • choices : selected values
    • selected : The initially selected value (NULL for no selection)
    • inline : horizontal or vertical
    • width

    It is also possible to add HTML.

    # Radio Button

    You can create a set of radio buttons used to select an item from a list.

    It's possible to change the settings :

    • selected : The initially selected value (character(0) for no selection)
    • inline : horizontal or vertical
    • width

    It is also possible to add HTML.

    library(shiny)
    
    ui <- fluidPage(    
      radioButtons("radio", 
                   label = HTML('<FONT color="red"><FONT size="5pt">Welcome</FONT></FONT><br> <b>Your favorite color is red ?</b>'),
                   choices = list("TRUE" = 1, "FALSE" = 2),
                   selected = 1,
                   inline = T,
                   width = "100%"),      
      fluidRow(column(3, textOutput("value")))) 
    
    
    server <- function(input, output){
      output$value <- renderPrint({
        if(input$radio == 1){return('Great !')}
         else{return("Sorry !")}})}
    
    shinyApp(ui = ui, server = server)
    
    

    enter image description here

    # Select box

    Create a select list that can be used to choose a single or multiple items from a list of values.

    library(shiny)
    
    ui <- fluidPage(    
      selectInput("id_selectInput", 
              label = HTML('<B><FONT size="3">What is your favorite color ?</FONT></B>'), 
              multiple = TRUE,
              choices = list("red" = "red", "green" = "green", "blue" = "blue", "yellow" = "yellow"), 
              selected = NULL),
      br(), br(),
      fluidRow(column(3, textOutput("text_choice")))) 
    
    
    server <- function(input, output){
      output$text_choice <- renderPrint({
        return(input$id_selectInput)})
    }
    
    shinyApp(ui = ui, server = server)
    
    

    enter image description here

    It's possible to change the settings :

    • label : title
    • choices : selected values
    • selected : The initially selected value (NULL for no selection)
    • multiple : TRUE or FALSE
    • width
    • size
    • selectize: TRUE or FALSE (for use or not selectize.js, change the display)

    It is also possible to add HTML.

    # Launch a Shiny app

    You can launch an application in several ways, depending on how you create you app. If your app is divided in two files ui.R and server.R or if all of your app is in one file.

    # 1. Two files app

    Your two files ui.R and server.Rhave to be in the same folder. You could then launch your app by running in the console the shinyApp() function and by passing the path of the directory that contains the Shiny app.

    shinyApp("path_to_the_folder_containing_the_files")  
    
    

    You can also launch the app directly from Rstudio by pressing the Run App button that appear on Rstudio when you an ui.R or server.R file open.
    ClicktoRun

    Or you can simply write runApp() on the console if your working directory is Shiny App directory.

    # 2. One file app

    If you create your in one R file you can also launch it with the shinyApp() function.

    • inside of your code :
    library(shiny)
    
    ui <- fluidPage() #Create the ui
    server <- function(input, output){} #create the server
    
    shinyApp(ui = ui, server = server) #run the App
    
    
    • in the console by adding path to a .R file containing the Shiny application with the paramter appFile:
    shinyApp(appFile="path_to_my_R_file_containig_the_app")
    
    

    # Debugging

    debug() and debugonce() won't work well in the context of most Shiny debugging. However, browser() statements inserted in critical places can give you a lot of insight into how your Shiny code is (not) working. See also: Debugging using browser()

    # Showcase mode

    Showcase mode displays your app alongside the code that generates it and highlights lines of code in server.R as it runs them.

    There are two ways to enable Showcase mode:

    • Launch Shiny app with the argument display.mode = "showcase", e.g., runApp("MyApp", display.mode = "showcase").
    • Create file called DESCRIPTION in your Shiny app folder and add this line in it: DisplayMode: Showcase.

    # Reactive Log Visualizer

    Reactive Log Visualizer provides an interactive browser-based tool for visualizing reactive dependencies and execution in your application. To enable Reactive Log Visualizer, execute options(shiny.reactlog=TRUE) in R console and or add that line of code in your server.R file. To start Reactive Log Visualizer, hit Ctrl+F3 on Windows or Command+F3 on Mac when your app is running. Use left and right arrow keys to navigate in Reactive Log Visualizer.

    # Control widgets

    Function Widget
    actionButton Action Button
    checkboxGroupInput A group of check boxes
    checkboxInput A single check box
    dateInput A calendar to aid date selection
    dateRangeInput A pair of calendars for selecting a date range
    fileInput A file upload control wizard
    helpText Help text that can be added to an input form
    numericInput A field to enter numbers
    radioButtons A set of radio buttons
    selectInput A box with choices to select from
    sliderInput A slider bar
    submitButton A submit button
    textInput A field to enter text
    library(shiny)
    
    # Create the UI
    ui <- shinyUI(fluidPage(
      titlePanel("Basic widgets"),
      
      fluidRow(
        
        column(3,
               h3("Buttons"),
               actionButton("action", label = "Action"),
               br(),
               br(), 
               submitButton("Submit")),
        
        column(3,
               h3("Single checkbox"),
               checkboxInput("checkbox", label = "Choice A", value = TRUE)),
        
        column(3, 
               checkboxGroupInput("checkGroup", 
                                  label = h3("Checkbox group"), 
                                  choices = list("Choice 1" = 1, 
                                                 "Choice 2" = 2, "Choice 3" = 3),
                                  selected = 1)),
        
        column(3, 
               dateInput("date", 
                         label = h3("Date input"), 
                         value = "2014-01-01"))   
      ),
      
      fluidRow(
        
        column(3,
               dateRangeInput("dates", label = h3("Date range"))),
        
        column(3,
               fileInput("file", label = h3("File input"))),
        
        column(3, 
               h3("Help text"),
               helpText("Note: help text isn't a true widget,", 
                        "but it provides an easy way to add text to",
                        "accompany other widgets.")),
        
        column(3, 
               numericInput("num", 
                            label = h3("Numeric input"), 
                            value = 1))   
      ),
      
      fluidRow(
        
        column(3,
               radioButtons("radio", label = h3("Radio buttons"),
                            choices = list("Choice 1" = 1, "Choice 2" = 2,
                                           "Choice 3" = 3),selected = 1)),
        
        column(3,
               selectInput("select", label = h3("Select box"), 
                           choices = list("Choice 1" = 1, "Choice 2" = 2,
                                          "Choice 3" = 3), selected = 1)),
        
        column(3, 
               sliderInput("slider1", label = h3("Sliders"),
                           min = 0, max = 100, value = 50),
               sliderInput("slider2", "",
                           min = 0, max = 100, value = c(25, 75))
        ),
        
        column(3, 
               textInput("text", label = h3("Text input"), 
                         value = "Enter text..."))   
      )
      
    ))
    
    # Create the server function
    server <- shinyServer(function(input, output){})
    
    # Run the app
    shinyApp(ui = ui, server = server)