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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().

This exercise is part of the course

Case Studies: Building Web Applications with Shiny in R

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Exercise instructions

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).

Hands-on interactive exercise

Have a go at this exercise by completing this sample code.

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)
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