“empty data message” in renderTable

问题

I user renderTable to show some data. However, sometimes the data table is empty, in which case I'd like to print "No data to show" or something similar. the default by renderTable is to show nothing for empty data. can this be changed? how?

回答1:

You can use a condition into a renderUi to render either a message or a "tableOutput" (you can't render directly the table)

datas <- data.frame()

shiny::runApp(list(
  ui = pageWithSidebar(
    headerPanel("Example"),
    sidebarPanel(
      selectInput("dataset", "Dataset", choices = c("iris", "datas"))
    ),
    mainPanel(
      uiOutput("ui")
    )
  ),
  server = function(input, output, session) {

    datasetInput <- reactive({
      switch(input$dataset,
             "iris" = iris,
             "datas" = datas)
    })

    output$ui <- renderUI({
      if(nrow(datasetInput()) == 0)
        return("No data to show")

      tableOutput("table")
    })

    output$table <- renderTable({
      head(datasetInput())
    })
  }
))

回答2:

I think you are looking for something like validate function.

Using example code provided by Julien:

    datas <- data.frame()

    shiny::runApp(list(

      ui = pageWithSidebar(

        headerPanel("Example"),

        sidebarPanel(
          selectInput("dataset", "Dataset", choices = c("iris", "datas"))
        ),

        mainPanel(
          tableOutput('table')
        )
      ),

      server = function(input, output, session) {

        datasetInput <- reactive({
          switch(input$dataset,
                 "iris" = iris,
                 "datas" = datas)
        })


        output$table <- renderTable({
          y <- head(datasetInput())
                validate(
                  need(nrow(y) > 0, "No Data to show")
                         )
        y
        })

      }

    ))

来源：https://stackoverflow.com/questions/22650737/empty-data-message-in-rendertable

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