r - Shiny :用一些文本描述或默认绘图替换 renderPlotly 错误

Question

我正在创建一个 Shiny 的应用程序，我想使用 brush功能。该应用程序目前看起来像:

在哪一个box()我收到错误 Error: argument 1 is not a vector .当用户对绘图进行刷选时，此错误就会消失。

如何将错误屏蔽为更用户友好的描述，例如“请选择上图的一个区域以生成此窗口...”。
剧情box()应该绘制用户选择，例如绘图的放大版本。
代码:

data <- mtcars



library(shiny)
library(shinydashboard)

header <- dashboardHeader(title = "My Dashboard")
sidebar <- dashboardSidebar(
    sidebarMenu(
        menuItem(text = "Main Menu", tabName = "MainPage")
    )
)
body <- dashboardBody(
    tabItems(
        tabItem(tabName = "MainPage",
                fluidRow(
                    box(
                        width = 12,
                        plotOutput("myPlot1", brush = "userSelectedSummaryStatistics")
                    )
                ),
                fluidRow(
                    box(
                        width = 4,
                        DT::dataTableOutput("userDefinedTable")
                    ),
                    box(
                        width = 8,
                        plotlyOutput("selectedUserDataFromUserDefinedTable")
                    )
                )
        )
    )
)


ui <- dashboardPage(
    header, sidebar, body
)

server <- function(input, output, session){
    output$myPlot1 <- renderPlot({
        data %>% 
            ggplot(aes(x = mpg, y = disp)) +
            geom_line()
    })
    
    selectedUserData = reactive({
        userSelectedSummaryStatistics = input$userSelectedSummaryStatistics
        userSelection = brushedPoints(data, userSelectedSummaryStatistics)
        return(userSelection)
    })
    
    output$userDefinedTable = DT::renderDataTable(DT::datatable(selectedUserData()))
    
    output$selectedUserDataFromUserDefinedTable <- renderPlotly({
        ggplotly(
            selectedUserData() %>% 
                ggplot(aes(x = mpg, y = disp)) +
                geom_line()
        )
    })
}


shinyApp(ui, server)

Answer 1

您可以使用 validate :

  output$selectedUserDataFromUserDefinedTable <- renderPlotly({
    validate(need(nrow(selectedUserData())>0,'Please select an area of the above plot in order to generate this window'))
    ggplotly(
      selectedUserData() %>% 
        ggplot(aes(x = mpg, y = disp)) +
        geom_line()
    )
  })