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Download the filtered data

Downloading files is achieved using the pair of functions downloadButton() and downloadHandler(). These two functions pair together similarly to how output and render functions are paired: downloadButton() determines where in the UI it will show up, while downloadHandler() needs to be saved into the output list and has the actual R code to create the downloaded file.

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Case Studies: Building Web Applications with Shiny in R

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Istruzioni dell'esercizio

Add the ability to download the data that is currently viewed in the table as a CSV file. Specifically:

  • Add a download button to the UI with ID "download_data" and a label of "Download".
  • Add a download handler to the server (line 31).
  • Give the downloaded file a name of "gapminder_data.csv" (line 33).
  • Write the filtered data into a CSV file (line 50).

Esercizio pratico interattivo

Prova a risolvere questo esercizio completando il codice di esempio.

ui <- fluidPage(
  h1("Gapminder"),
  sliderInput(inputId = "life", label = "Life expectancy",
              min = 0, max = 120,
              value = c(30, 50)),
  selectInput("continent", "Continent",
              choices = c("All", levels(gapminder$continent))),
  # Add a download button
  ___(outputId = ___, label = ___),
  plotOutput("plot"),
  tableOutput("table")
)

server <- function(input, output) {
  output$table <- renderTable({
    data <- gapminder
    data <- subset(
      data,
      lifeExp >= input$life[1] & lifeExp <= input$life[2]
    )
    if (input$continent != "All") {
      data <- subset(
        data,
        continent == input$continent
      )
    }
    data
  })

  # Create a download handler
  output$download_data <- ___(
    # The downloaded file is named "gapminder_data.csv"
    filename = ___,
    content = function(file) {
      # The code for filtering the data is copied from the
      # renderTable() function
      data <- gapminder
      data <- subset(
        data,
        lifeExp >= input$life[1] & lifeExp <= input$life[2]
      )
      if (input$continent != "All") {
        data <- subset(
          data,
          continent == input$continent
        )
      }
      
      # Write the filtered data into a CSV file
      write.csv(___, file, row.names = FALSE)
    }
  )

  output$plot <- renderPlot({
    data <- gapminder
    data <- subset(
      data,
      lifeExp >= input$life[1] & lifeExp <= input$life[2]
    )
    if (input$continent != "All") {
      data <- subset(
        data,
        continent == input$continent
      )
    }
    ggplot(data, aes(gdpPercap, lifeExp)) +
      geom_point() +
      scale_x_log10()
  })
}

shinyApp(ui, server)
Modifica ed esegui il codice