Question

我是新手，我正在尝试做一个简单的密度图，其中有2组数据，平均值带有反应性“偏移”等。对此的简化总结是，一组数据的平均值为0，方差为1。第二组数据的平均值为shift，在滑块中定义。

我尝试使用reactiveValues，如下面的代码所示，以存储从d1函数y值生成的观测矩阵density，并且相应的x值是存储在x中。


library(shiny)

# Define UI for application that draws a histogram
ui <- fluidPage(

   # Application title
   titlePanel("Old Faithful Geyser Data"),

   # Sidebar with a slider input for number of bins 
   sidebarLayout(
      sidebarPanel(
         sliderInput("shift",
                     "shift of 2nd set",
                     min = -1,
                     max = 1,
                     value = 0)
      ),

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

# Define server logic required to draw a histogram
server <- function(input, output) {
   data <- reactiveValues({

     d1 <- matrix(nrow=100, ncol=512)
     for(i in 1:70){
       d1[i,] <- density(rnorm(1000),from = -3, to = 3)$y
     }
     for(i in 71:100){
       d1[i,] <- density(rnorm(1000, input$shift),from = -3, to = 3)$y
     }
     x <- density(rnorm(1000),from = -3, to = 3)$x

   })
   output$distPlot <- renderPlot({
      matplot(data$x, t(data$d1), type = "l", lty = 1, col = c(rep(1,70),rep(2,30)))
   })
}

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

上面的代码主要来自示例闪亮应用程序，因此请原谅任何通用引用。应该仍然可以使用。

我期待的是一个明亮的情节，左边有一个滑块，而右边的情节有2种颜色的100条密度线。更改shift滑块后，第二组数据（红色）将根据移位向左或向右滑动。

相反，我收到错误消息

  55: stop
  54: .getReactiveEnvironment()$currentContext
  53: .subset2(x, "impl")$get
  52: $.reactivevalues
  47: server [/beavis/Documents/test/app.R#37]
Error in .getReactiveEnvironment()$currentContext() : 
  Operation not allowed without an active reactive context. (You tried to do something that can only be done from inside a reactive expression or observer.)

有人可以帮助我修复此代码吗？任何帮助将不胜感激。玩了一个小时，我相信问题出在reactiveValues部分，但是到目前为止没有任何效果。

Answer 1

很好尝试。你很亲密您缺少的是两件事。您正在创建一个data对象，该对象将成为反应对象（我改用reactive）。这意味着每当您呼叫data时，都需要将其称为data()。

第二，您的data仅返回x。在您的情况下，此反应性环境的输出应为x和d1的列表。

library(shiny)

# Define UI for application that draws a histogram
ui <- fluidPage(

  # Application title
  titlePanel("Old Faithful Geyser Data"),

  # Sidebar with a slider input for number of bins
  sidebarLayout(
    sidebarPanel(
      sliderInput("shift",
                  "shift of 2nd set",
                  min = -1,
                  max = 1,
                  value = 0, 
                  step = 0.1)  # I added a step
    ),

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

# Define server logic required to draw a histogram
server <- function(input, output) {
  # This reactive environment can be accessed using data().
  data <- reactive({
    d1 <- matrix(nrow=100, ncol=512)
    for(i in 1:70){
      d1[i,] <- density(rnorm(1000),from = -3, to = 3)$y
    }
    for(i in 71:100){
      d1[i,] <- density(rnorm(1000, input$shift),from = -3, to = 3)$y
    }
    x <- density(rnorm(1000), from = -3, to = 3)$x
    list(x = x, d1 = d1)  # make sure that all objects are returned
  })

  output$distPlot <- renderPlot({
    matplot(data()$x, t(data()$d1), type = "l", lty = 1, col = c(rep(1,70),rep(2,30)))
  })
}

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

代码以在Shiny中绘制反应式表格

1 个答案: