闪亮随机默认

Question

我有兴趣为每次刷新页面时更改的闪亮应用程序设置默认选项。所以例如，在hello world Shiny演示中，我希望它是500而不是默认选择sample(1:1000,1)

http://shiny.rstudio.com/gallery/example-01-hello.html

我已经尝试将随机生成的值直接放在value =部分，但这似乎只在每次启动应用程序时更新，而不是每次加载页面时。

如何进行随机默认设置？

Answer 1

我们可以使用updateSliderInput，例如

server <- function(input, output, session) {
  observe({
    updateSliderInput(session, "bins", value = sample(1:500,1))
  })

 ....
}

不要忘记将session变量添加到服务器函数定义，并将sliderInput中的max值更新为500。

Answer 2

您需要使用响应式UI元素。

library(shiny)

ui <- fluidPage(

  # Application title
  titlePanel("Hello Shiny!"),

  # Sidebar with a slider input for number of observations
  sidebarLayout(
    sidebarPanel(
uiOutput("slider")
    ),

    # Show a plot of the generated distribution
    mainPanel(
      plotOutput("distPlot")
    )
  )
)


server <- function(input, output) {

  # Expression that generates a plot of the distribution. The expression
  # is wrapped in a call to renderPlot to indicate that:
  #
  #  1) It is "reactive" and therefore should be automatically 
  #     re-executed when inputs change
  #  2) Its output type is a plot 
  #

  output$slider <- renderUI({
    sliderInput("obs", 
                "Number of observations:", 
                min = 1, 
                max = 1000, 
                value =runif(1,1,1000))

  })
  output$distPlot <- renderPlot({
    req(input$obs)
    # generate an rnorm distribution and plot it
    dist <- rnorm(input$obs)
    hist(dist)
  })
}

  shinyApp(ui = ui, server = server)

这将在滑块中随机选择一个新值。这是你追求的吗？