LoslegenKostenlos loslegen

Create a new word cloud on demand

After isolating the word cloud render code so that it wouldn't update too often, the last step is to provide a way to render the word cloud only when the user chooses to. This can be achieved with the help of an actionButton().

Diese Übung ist Teil des Kurses

Case Studies: Building Web Applications with Shiny in R

Kurs anzeigen

Anleitung zur Übung

Your task is to add a button to the Shiny app, and re-render the word cloud when the button gets pressed. Specifically:

  • Add an action button to the app with an input ID of "draw" and a label of "Draw!" (line 26).
  • Add the button as a dependency in the word cloud rendering function so that the word cloud will re-run when the button is pressed (line 56).

Interaktive Übung

Versuche dich an dieser Übung, indem du diesen Beispielcode vervollständigst.

ui <- fluidPage(
  h1("Word Cloud"),
  sidebarLayout(
    sidebarPanel(
      radioButtons(
        inputId = "source",
        label = "Word source",
        choices = c(
          "Art of War" = "book",
          "Use your own words" = "own",
          "Upload a file" = "file"
        )
      ),
      conditionalPanel(
        condition = "input.source == 'own'",
        textAreaInput("text", "Enter text", rows = 7)
      ),
      conditionalPanel(
        condition = "input.source == 'file'",
        fileInput("file", "Select a file")
      ),
      numericInput("num", "Maximum number of words",
                   value = 100, min = 5),
      colourInput("col", "Background color", value = "white"),
      # Add a "draw" button to the app
      ___(inputId = ___, label = ___)
    ),
    mainPanel(
      wordcloud2Output("cloud")
    )
  )
)

server <- function(input, output) {
  data_source <- reactive({
    if (input$source == "book") {
      data <- artofwar
    } else if (input$source == "own") {
      data <- input$text
    } else if (input$source == "file") {
      data <- input_file()
    }
    return(data)
  })
  
  input_file <- reactive({
    if (is.null(input$file)) {
      return("")
    }
    readLines(input$file$datapath)
  })
  
  output$cloud <- renderWordcloud2({
    # Add the draw button as a dependency to
    # cause the word cloud to re-render on click
    input$___
    isolate({
      create_wordcloud(data_source(), num_words = input$num,
                       background = input$col)
    })
  })
}

shinyApp(ui = ui, server = server)
Code bearbeiten und ausführen