如何在Shiny仪表板中创建条件renderUI

Question

我无法通过renderMenu创建条件侧边栏菜单，因为if语句失败。 “警告：if：参数长度为零时出错”。

我在Shiny仪表板中发现了有条件的RenderUI R闪亮和有条件的面板，但是我都没有找到。 在这种情况下，可以使用条件面板，但从长远来看，我将需要能够在服务器端进行操作。

    if (interactive()) {
  library(ggplot2)
  library(shiny)
  library(shinydashboard)
  library(shinipsum)

  ui <- dashboardPage(
    header = dashboardHeader(),
    dashboardSidebar(
      sidebarMenuOutput("plotDataVHA"),
      sidebarMenuOutput("tabSelector")
    ),
    dashboardBody(tabItems(
      tabItem(tabName = "facilities",
              fluidRow(box(
                uiOutput("selectedFacilityTime")
              ))),
      tabItem(tabName = "service",
              fluidRow(box(
                uiOutput("selectedFacilityYyCases")
              )))
    ))
  )

  server <- function(input, output) {
    output$renderedSelectedFacilityTime <- renderPlot({
      random_ggplot(type = "line")
    })
    output$selectedFacilityTime <- renderUI({
      plotOutput("renderedSelectedFacilityTime")
    })

    output$renderedFacilityYyCases <- renderPlot({
      random_ggplot(type = "bar")
    })
    output$selectedFacilityYyCases <- renderUI({
      plotOutput("renderedFacilityYyCases")
    })

    output$tabSelector <- renderMenu({
      sidebarMenu(id = "test",
                  menuItem(
                    text = "Chart data",
                    menuSubItem(
                      text = "Facilities",
                      tabName = "facilities",
                      selected = TRUE
                    ),
                    menuSubItem(
                      text = "Service & Specialty",
                      tabName = "service",
                      icon = NULL
                    )
                  ))
    })

    output$plotDataVHA <- renderMenu({
      if (input$test == "facilities") {
      sidebarMenu(
        menuItem(
          text = "VHA data",
          menuSubItem(
            text = "None",
            selected = TRUE,
            icon = NULL
          ),
          menuSubItem(text = "Mean", icon = NULL)
        )
      )
    }
     })
  }

  shinyApp(ui, server)
}

正常工作时，只有在选择了“设施”子菜单时，菜单“ VHA数据”才可见。

Answer 1

有趣的问题。 得到argument is of length zero的原因argument is of length zero错误是因为您正在通过renderMenu()在服务器端渲染两个菜单。 因此，当应用程序启动时， input$test没有分配值。 您可以通过使用req()来避免这种情况，该req()仅在启动input$test之后才评估测试input$test == "facilities" 。

现在，仅当选择了另一个子菜单时菜单才出现，您想要独立于renderMenu()创建菜单。 这是更好地评估在正常条件下reactive()然后通过该反应性功能作为输入到renderMenu() 最后，要在input$test == "facilities"为FALSE时删除菜单，可以呈现一个空的html容器。

这是更新的代码：

  library(ggplot2)
  library(shiny)
  library(shinydashboard)
  library(shinipsum)

  ui <- dashboardPage(
    header = dashboardHeader(),
    dashboardSidebar(
      sidebarMenuOutput("plotDataVHA"),
      sidebarMenuOutput("tabSelector")
    ),
    dashboardBody(tabItems(
      tabItem(tabName = "facilities",
              fluidRow(box(
                uiOutput("selectedFacilityTime")
              ))),
      tabItem(tabName = "service",
              fluidRow(box(
                uiOutput("selectedFacilityYyCases")
              )))
    ))
  )

  server <- function(input, session, output) {
    output$renderedSelectedFacilityTime <- renderPlot({
      random_ggplot(type = "line")
    })
    output$selectedFacilityTime <- renderUI({
      plotOutput("renderedSelectedFacilityTime")
    })

    output$renderedFacilityYyCases <- renderPlot({
      random_ggplot(type = "bar")
    })
    output$selectedFacilityYyCases <- renderUI({
      plotOutput("renderedFacilityYyCases")
    })

    output$tabSelector <- renderMenu({
      sidebarMenu(id = "test",
                  menuItem(
                    text = "Chart data",
                    menuSubItem(
                      text = "Facilities",
                      tabName = "facilities",
                      selected = TRUE
                    ),
                    menuSubItem(
                      text = "Service & Specialty",
                      tabName = "service",
                      selected = FALSE,
                      icon = NULL
                    )
                  ))
    })

    make_menu <- reactive({
      cat("Current submenu selected: ", input$test, "\n\n")

      if (req(input$test) == "facilities") {
      sidebarMenu(
        menuItem(
          text = "VHA data",
          menuSubItem(
            text = "None",
            selected = TRUE,
            icon = NULL
          ),
          menuSubItem(text = "Mean", icon = NULL)
        )
      )
      } else {
        # return an empty HTML container
        div()
      } 
    })

    output$plotDataVHA <- renderMenu({
        make_menu()
    })

  }

  shinyApp(ui, server)