1 Your first Shiny app

1.8 Exercises

library(shiny)

ui <- fluidPage(
    textInput("name", "What's your name?"),
    textOutput("greeting")
)

server <- function(input, output, session) {
    output$greeting <- renderText({
        paste0("Hello ", input$name)
    })
}

shinyApp(ui, server)

library(shiny)

ui <- fluidPage(
    sliderInput("x", label = "If x is", min = 1, max = 50, value = 30),
    "then x times 5 is",
    textOutput("product")
)

server <- function(input, output, session) {
    output$product <- renderText({ 
      # Fixed error
       input$x * 5
      # by adding input$ 
    })
}

shinyApp(ui, server)

library(shiny)

ui <- fluidPage(
    sliderInput("x", label = "If x is", min = 1, max = 50, value = 30),
    sliderInput("y", label = "and y is", min = 1, max = 50, value = 30),
    "then x times y is",
    textOutput("product")
)

server <- function(input, output, session) {
    output$product <- renderText({ 
       input$x * input$y
    })
}

shinyApp(ui, server)

library(shiny)

ui <- fluidPage(
    sliderInput("x", "If x is", min = 1, max = 50, value = 30),
    sliderInput("y", "and y is", min = 1, max = 50, value = 5),
    "then, (x * y) is", textOutput("product"),
    "and, (x * y) + 5 is", textOutput("product_plus5"),
    "and (x * y) + 10 is", textOutput("product_plus10")
)

server <- function(input, output, session) {
    # Add this reactive expression to reduce 
    # amount of duplicated code
    product <- reactive({
        input$x * input$y
    })
    output$product <- renderText({ 
        product()
    })
    output$product_plus5 <- renderText({ 
        product() + 5
    })
    output$product_plus10 <- renderText({ 
        product() + 10
    })
}

shinyApp(ui, server)

• What’s new is the additional calculation where 5 and 10 were added to the product and the outputs rendered as text.

library(shiny)
library(ggplot2)

datasets <- c("economics", "faithfuld", "seals")

ui <- fluidPage(
    selectInput("dataset", "Dataset", choices = datasets),
    verbatimTextOutput("summary"),
    # 1st Bug: tableOutput -> plotOutput
    plotOutput("plot")
)

server <- function(input, output, session) {
    dataset <- reactive({
        get(input$dataset, "package:ggplot2")
    })
    # 2nd Bug: Spelling
    output$summary <- renderPrint({
        summary(dataset())
    })
    output$plot <- renderPlot({
      # 3rd Bug: dataset -> dataset() 
        plot(dataset())
    }, res = 96)
}

shinyApp(ui, server)