Accessing/using reactive list problem.

shiny
1

Dear all

After some hours trying to figure out myself what the error is, I give up.

I want to save a confidence interval, a vector, in a reactiveValue. But when I want to use this inside a renderUI inside a renderPlot i get into trouble.

I have tried to cut away as much as possible to make my example minimal, which I doubt it is but you surely get this idea quickly.

Any help is much appreciated. I would very much like to LEARN why this error is occurring, not just fix it (as I already made a work around)

best


library(shiny)
library(ggplot2)

# Define UI for application that draws a histogram
ui <- fluidPage(
  
  # Application title
  titlePanel("Screening failures"),
  
  # Sidebar with a slider input for number of bins 
  sidebarLayout(
    sidebarPanel(
      numericInput("screened",
                   "Number of Subjects finished screening",
                   min = 1,
                   max = 2000,
                   value = 107)
      ,
      numericInput("failures",
                   "Number of screening failures",
                   min = 1,
                   max = 200,
                   value = 88)
      ,
      uiOutput("freq_CI")
      ,
      uiOutput("sf_slider")
      ,
      numericInput("n_in_screening", label = "In Screening", min = 0, max = 200, value = 51)
      ),
    
    
    # Show a plot of the generated distribution
    mainPanel(
      plotOutput("binom_plot"),
      verbatimTextOutput("text3"),
      uiOutput("info_text_lowerCI")
      )
  )
)

# Define server logic required to draw a histogram
server <- function(input, output) {
  
  #create reactive value for use across renderfuns
  df <- reactiveValues()
  
  #UI rate slider
  output$sf_slider <- renderUI({
    
    n_screen <- input$screened
    n_fail <- input$failures
    
    sliderInput(inputId = "sf_rate", label = "SF rate, adjustable", min = 0, max = 1, value = n_fail/n_screen)
    
  })
  
  output$freq_CI <- renderUI({
    req(input$sf_rate)
    
    p_hat <- as.numeric(input$sf_rate)
    n   <- input$screened
    n_s <- input$failures
    n_f <- n - n_s
    z <- qnorm(p = 1-0.05/2)
    
    Wil_CI <- (p_hat + z^2/(2*n))/(1 + z^2/n) + c(-1,1)*z/(1 + z^2/n)*sqrt(p_hat*(1-p_hat)/n + z^2/(4*n^2))
    Wil_CI <- round(Wil_CI, 3)
    
    df$CI <- Wil_CI
    p("hello, lower is available -> ", df$CI[1])

  })
  
  #Test
  output$text3 <- renderPrint({
    #This works
    df$CI
  })
  
  output$target_slider <- renderUI({
    target <- input$target
    
    sliderInput(inputId = "range", label = "Range around target. Both values included.", min = -10 + target, max = target + 20, value = c(-2 + target, 5 + target))
    
  })
  

  
  output$binom_plot <- renderPlot({
    req(input$sf_rate)
    
    n_in_screening <- input$n_in_screening
    p_randomised <- 1-input$sf_rate
    n_randomised <- input$screened - input$failures
    
    
    n_vek <- n_randomised + (0:n_in_screening)
    p_vek <- dbinom(x = 0:n_in_screening, size = n_in_screening, prob = p_randomised)
    #I can access the reactive variable here just fine;
    p_vek2 <- dbinom(x = 0:n_in_screening, size = n_in_screening, prob = df$CI[1])
    p_vek3 <- dbinom(x = 0:n_in_screening, size = n_in_screening, prob = df$CI[2])
    
    

    df <- data.frame(x = rep(n_vek,3), y = c(p_vek,p_vek2,p_vek3))
    
    p <- ggplot(data = df, aes(x = x, y = y)) + geom_segment(aes(x = x, xend = x, y = 0, yend = y))

    #Probabilities given lower CI, i.e. best case
    output$info_text_lowerCI <- renderUI({
      print(df$CI) #This prints NULL
      print(df$CI[1])#Also NULL
      tagList(
        h3("I would like to display/USE Lower limit here ->>>",df$CI[1]),
      )
      
    })
    
    #return plot
    p
  })
  
  
}

# Run the application 
shinyApp(ui = ui, server = server)
2

Don't reuse df, and move output$info_text_lowerCI outside. Each output$ must be at the same level. output is a like a list. Putting output$ inside another output$ definition doesn't make sense, it will apply to some temporary local variable called output.

	output$binom_plot <- renderPlot({
		req(input$sf_rate)

		n_in_screening <- input$n_in_screening
		p_randomised <- 1-input$sf_rate
		n_randomised <- input$screened - input$failures


		n_vek <- n_randomised + (0:n_in_screening)
		p_vek <- dbinom(x = 0:n_in_screening, size = n_in_screening, prob = p_randomised)
		#I can access the reactive variable here just fine;
		p_vek2 <- dbinom(x = 0:n_in_screening, size = n_in_screening, prob = df$CI[1])
		p_vek3 <- dbinom(x = 0:n_in_screening, size = n_in_screening, prob = df$CI[2])

		temp <- data.frame(x = rep(n_vek,3), y = c(p_vek,p_vek2,p_vek3))

		p <- ggplot(data = temp, aes(x = x, y = y)) + geom_segment(aes(x = x, xend = x, y = 0, yend = y))

		#return plot
		p
	})

	#Probabilities given lower CI, i.e. best case
	output$info_text_lowerCI <- renderUI({
		print(df$CI) #This prints NULL
		print(df$CI[1])#Also NULL
		tagList(
			h3("I would like to display/USE Lower limit here ->>>",df$CI[1]),
		)

	})
3

Thanks for your reply!

Could you please elaborate?
br

4

You have df as your reactive list and also use df as a local variable inside output$binom_plot. That's confusing.

5

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