R Shiny应用程序延迟执行

Question

是否可能让RShiny应用程序的某些部分以延迟的方式执行，就像Windows服务中的延迟启动一样？

让我详细说明。

我有一个带标签的闪亮应用程序。每个选项卡的边栏面板上都有一堆单选按钮。单击每个单选按钮会显示一个报告。我的设置就这么简单。

然而，当我每次加载应用程序时，当第一个选项卡自动呈现时，与该选项卡下的所有单选按钮关联的所有报告都会被执行，然后选择第一个单选按钮并显示其关联报告。整个过程大约需要10-11秒，我想把它记下来。

在服务器启动期间，我只需读取全局中的myData.RData文件。R。所以在服务器启动期间，所有数据都是预先提取的（我假设保存在内存中）。当选项卡聚焦时，会读取myData.RData中的data.frame，并调用一系列ggplots（renderPlot）和表（renderText）。

有没有一种方法可以在几秒钟内呈现第一个报告，然后继续执行其他ggplot和表？我确实经历了反应性导体和隔离，但不知道什么解决方案适合我的问题。

或者有其他方法可以加快加载（和刷新）时间吗？

一些有助于理解问题的代码。。

    # In server.R
    library(shiny)
    library(plyr)
    library(ggplot2)
    library(grid)
    source("a.R", local=TRUE)
    source("b.R", local=TRUE)
    shinyServer(function(input, output) {
      # The below two lines represent a report pair to me. So I have a Bar plot and the associated Table report.
      output$wSummaryPlot = renderPlot({ print(drawBarPlotA("Bar Plot A")) })
      output$wSummaryTable = renderText({ tableA() })
      # There are about 20 such pairs in server.R  
      # Please note that I am including other R file by "source". The first two lines shows that. Don't know if that is what is causing the problem.
      # The drawBarPlotA and tableA are functions defined in one of the source files which are included above. 
      # There are 5 such files which are included similarly.
    })
    # In ui.R
    shinyUI(pageWithSidebar(
        headerPanel(windowTitle = "Perfios - DAS", addHeader()),
        sidebarPanel(
            conditionalPanel(condition = "input.reportTabs == 1 && input.reportType == 'reportTypeA'",
                         wellPanel(radioButtons("showRadio", strong("Attributes:"),
                                                c("Analysis A" = "a", 
                                                  "Analysis B" = "b", 
                                                  "Analysis C" = "c", 
                                                  "Analysis D" = "d",
                                                  "Analysis E" = "e",
                                                  "Analysis F" = "f"
                                                  )))
        ))
        mainPanel(
            tabPanel("A", value = "1", 
                 conditionalPanel(condition = "input.reportType == 'reportTypeA'",
                                  conditionalPanel(condition = "showRadio == 'X'", 
                                                   plotOutput("wSummaryPlot"), h4("Summary:"), verbatimTextOutput("wSummaryTable"))

       # Many such element here to accomodate for those 20 reports... 
    )))
))
# In drawBarPlotA
drawBarPlotA = function(mainText) {
  ggplot(data, aes(variable, value, fill = some_fill)) + 
    geom_bar(stat = "identity", position = "dodge", color = "grey") +
    ylab("Y Label") + 
    xlab(NULL) + 
    theme_bw() + 
    ggtitle(mainText) + 
    scale_fill_brewer(palette = "Set1") +
    annotate("text", x = 1.2, y = 0, label = "Copyright...", size = 4) +
    theme(axis.text.x = element_text(angle = 45, hjust = 1, size = "12", face = "bold"), 
          axis.text.y = element_text(size = "12"),
          plot.title = element_text(size = "14", vjust = 3, face = "bold"))  
}
tableA = function() {
  # This is a data.frame which is returned
  data
}

Answer 1

shinyServer(function(input, output, session) {
  values <- reactiveValues(starting = TRUE)
  session$onFlushed(function() {
    values$starting <- FALSE
  })
  output$fast <- renderText({ "This happens right away" })
  output$slow <- renderText({
    if (values$starting)
      return(NULL)
    "This happens later"
  })
})