r - Shiny アプリで不要な負荷を避ける

Question

eventReactive2 つのデータセットを読み込む関数があります。各データセットを選択できますが、両方とも同じ 内にロードされますeventReactive。ただし、ユーザーが 2 つのデータセットの 1 つだけを変更した場合、両方をロードするのではなく、変更されたデータセットのみをロードする必要があります。2 つのアクション ボタンを使用すると、これがはるかに簡単になることはわかっていますが、1 つにする必要があります。以下のサンプルコードを見つけてください。

したがって、この例では、変数が変更されたコードのその部分のみを再度実行したいと考えています。ui.r:

library(shiny)

# Define UI for dataset viewer application
shinyUI(fluidPage(

  # Application title
  titlePanel("Reactivity"),

  # Sidebar with controls to provide a caption, select a dataset,
  # and specify the number of observations to view. Note that
  # changes made to the caption in the textInput control are
  # updated in the output area immediately as you type
  sidebarLayout(
    sidebarPanel(
      textInput("caption", "Caption:", "Data Summary"),
      actionButton('Go','Go'),

      selectInput("dataset", "Choose a dataset:", 
                  choices = c("rock", "pressure", "cars")),
      selectInput("dataset2", "Choose a dataset:", 
                  choices = c("rock", "pressure", "cars")),

      numericInput("obs", "Number of observations to view:", 10)
    ),


    # Show the caption, a summary of the dataset and an HTML 
     # table with the requested number of observations
    mainPanel(
      h3(textOutput("caption", container = span)),
      verbatimTextOutput('one'),
      verbatimTextOutput('two'),
      verbatimTextOutput("summary"), 

      verbatimTextOutput("summary2")#, 

      # tableOutput("view"),
      # tableOutput("view2")
    )
  )
))

server.r

library(shiny)
library(datasets)

# Define server logic required to summarize and view the selected
# dataset
shinyServer(function(input, output) {

  # By declaring datasetInput as a reactive expression we ensure 
  # that:
  #
  #  1) It is only called when the inputs it depends on changes
  #  2) The computation and result are shared by all the callers 
  #   (it only executes a single time)
  #
  datasetInput <- eventReactive(input$Go,{

    ##Only run if input$dataset has changed##
    withProgress(message='Loading 1:This should take very long....',value=0,{
      for(i in 1:5){
        Sys.sleep(1)
        incProgress(i/5)
      }
    x<-switch(input$dataset,
           "rock" = rock,
           "pressure" = pressure,
           "cars" = cars)

    })
###only run if input$dataset2 has changed
    withProgress(message='Loading 2:This should take even longer....',value=0,{
      for(i in 1:5){
        Sys.sleep(1.5)
        incProgress(i/5)
      }       
      y<-switch(input$dataset2,
                         "rock" = rock,
                         "pressure" = pressure,
                         "cars" = cars)
    })




    return(list(x=x,y=y,input1=input$dataset,input2=input$dataset2))
  })

  # The output$caption is computed based on a reactive expression
  # that returns input$caption. When the user changes the
  # "caption" field:
  #
  #  1) This function is automatically called to recompute the 
  #     output 
  #  2) The new caption is pushed back to the browser for 
  #     re-display
  # 
  # Note that because the data-oriented reactive expressions
  # below don't depend on input$caption, those expressions are
  # NOT called when input$caption changes.
  output$caption <- renderText({
    input$caption
  })

  # The output$summary depends on the datasetInput reactive
  # expression, so will be re-executed whenever datasetInput is
  # invalidated
  # (i.e. whenever the input$dataset changes)
  output$summary <- renderPrint({
    dataset <- datasetInput()$x
    summary(dataset)
  })

  output$summary2 <- renderPrint({
    dataset <- datasetInput()$y
    summary(dataset)
  })

  # The output$view depends on both the databaseInput reactive
  # expression and input$obs, so will be re-executed whenever
  # input$dataset or input$obs is changed. 
  output$view <- renderTable({
    head(datasetInput()$x, n = input$obs)
  })
  output$view2 <- renderTable({
    head(datasetInput()$y, n = input$obs)
  })
  output$one<-renderText(datasetInput()$input1)
  output$two<-renderText(datasetInput()$input2)

})

私はすでにこのようなことを試しました:if(datasetInput()$input1 != input$dataset){execute...} しかし、おそらく同じ関数で作成されたリアクティブ関数内の値を使用しているため、機能しません...