如何在 R 闪亮的 for 循环内更新反应性输出 [英] How to update reactive output inside a for loop in R shiny

问题描述

我是 Shiny 的新手，遇到了一个我找不到答案的问题.基本上，我有一个 Shiny 应用程序，它在循环中进行一些长时间的计算，我希望它每隔几次迭代就输出一个进度报告".然而，即使我在循环中重新分配了我的反应变量，输出也不会更新，直到循环(或整个函数?)完成.

这是我的意思的简化测试用例:

图书馆(闪亮)# 基本界面ui <-流体页面(动作按钮(运行"，运行")，文本输出(文本框"))# 带循环的基本服务器服务器 <- 功能(输入，输出){textvals=reactiveValues(a=0)观察事件(输入$运行，{for(i 在 1:10){textvals$a=i # 期望输出在这里更新，但不会Sys.sleep(0.1) # 轻微的暂停所以不是瞬间的}})output$textbox <- renderText({文本值$a})}# 运行应用程序闪亮应用(用户界面 = 用户界面，服务器 = 服务器)

我期望的是，当循环执行时，显示会更新 1, 2, 3, ... 10.相反，它只是直接从 0 跳转到 10.如何在循环中途强制更新?

谢谢.

解决方案

使用 invalidateLater 你可以得到一些接近你想要的东西.我认为这不是最短的方法，但它可以帮助您找到更好的解决方案.

图书馆(闪亮)# 基本界面ui <-流体页面(动作按钮(运行"，运行")，文本输出(文本框"))# 带循环的基本服务器服务器 <- 功能(输入，输出，会话){textvals <-reactiveVal(0)主动 <-reactiveVal(FALSE)output$textbox <- renderText({文本值()})观察({invalidateLater(1000，会话)隔离({如果(活动()){textvals(textvals() + 1)如果(textvals()> 9){活动(假)}}})})观察事件(输入$运行，{活动(真)})}# 运行应用程序闪亮应用(用户界面 = 用户界面，服务器 = 服务器)

顺便说一下，reactive 和 for 循环不太好相处.这可能会有所帮助:https://gist.github.com/bborgesr/e1ce7305f914f9ca762ea6>

I'm new to Shiny and have hit a problem I can't find an answer for. Basically, I have a Shiny app that does some long calculations in a loop and I want it to output a "progress report" every few iterations. However, even though I reassign my reactive variable within the loop, the output doesn't update until the loop (or entire function?) has finished.

Here is a simplified test case of what I mean:

library(shiny)

# Basic interface
ui <- fluidPage(
     actionButton("run", "Run"),
     textOutput("textbox")
)

# Basic server with loop
server <- function(input, output) {

  textvals=reactiveValues(a=0)

  observeEvent(input$run, {
    for(i in 1:10){
      textvals$a=i   # Expect output to update here, but doesn't
      Sys.sleep(0.1) # Slight pause so isn't instantaneous
    }
  })

   output$textbox <- renderText({
      textvals$a
   })
}

# Run the application 
shinyApp(ui = ui, server = server)

What I would expect is that the display would update 1, 2, 3, ... 10 as the loop executes. Instead, it just jumps straight from 0 to 10. How can I force an update partway through the loop?

Thank you.

解决方案

With using invalidateLater you can get something closed to what you want. Not the shortest way to do it I think, but it may help you to find a better solution.

library(shiny)

# Basic interface
ui <- fluidPage(
  actionButton("run", "Run"),
  textOutput("textbox")
)

# Basic server with loop
server <- function(input, output, session) {

  textvals <- reactiveVal(0)
  active <- reactiveVal(FALSE)

  output$textbox <- renderText({
   textvals()
  })

  observe({
    invalidateLater(1000, session)
    isolate({
      if (active()) {
        textvals(textvals() + 1)
        if (textvals() > 9) {
          active(FALSE)
        }
      }
    })
  })

  observeEvent(input$run, {
    active(TRUE)
  })
}

# Run the application 
shinyApp(ui = ui, server = server)

By the way, reactive and for loops don't really get on well. This may help : https://gist.github.com/bborgesr/e1ce7305f914f9ca762c69509dda632e

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