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Fit a smooth curve: checkbox input

Unlike text and numeric inputs, checkbox inputs are limited to only two possible values: TRUE or FALSE. When the user checks a checkbox input, the input has a value of TRUE, and if the box is unchecked then it returns FALSE.

Note that the value parameter of the checkboxInput() function, which defines the initial value, can only be set to either TRUE or FALSE.

The code for the Shiny app from the last exercise is provided with some modification. The ggplot plot object inside renderPlot() is now assigned to a variable p.

Diese Übung ist Teil des Kurses

Case Studies: Building Web Applications with Shiny in R

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Anleitung zur Übung

Your task is to add a checkbox input that, when checked, will add a line of best fit to the plot. Specifically:

  • Add a checkbox input to the UI with ID "fit", a label of "Add line of best fit", and an initial state of being unchecked.
  • Add code to the server so that when the input is checked, a line of best fit is added to the plot. The code for adding a line of best fit is provided (line 26).

Interaktive Übung

Vervollständige den Beispielcode, um diese Übung erfolgreich abzuschließen.

# Define UI for the application
ui <- fluidPage(
  sidebarLayout(
    sidebarPanel(
      textInput("title", "Title", "GDP vs life exp"),
      numericInput("size", "Point size", 1, 1),
      # Add a checkbox for line of best fit
      ___
    ),
    mainPanel(
      plotOutput("plot")
    )
  )
)

# Define the server logic
server <- function(input, output) {
  output$plot <- renderPlot({
    p <- ggplot(gapminder, aes(gdpPercap, lifeExp)) +
      geom_point(size = input$size) +
      scale_x_log10() +
      ggtitle(input$title)
    
    # When the "fit" checkbox is checked, add a line
    # of best fit
    if (___) {
      p <- p + geom_smooth(method = "lm")
    }
    p
  })
}

# Run the application
shinyApp(ui = ui, server = server)
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