Response to StackOverflow R (Shiny) question around Automating interaction. (2 files)

server.R

library(shiny)

updates <- 0
updater <- function(updates){ updates + 1 }

shinyServer(function(input,output, session){                                       

    
  updateTracker <- reactive( { 
    invalidateLater(as.numeric(input$secPause) * 1000, session)
    updates <<- as.numeric(updater(updates))
  })
  
  autoControl <- reactive( {
    if(updateTracker() <= 5)
      secPause <<- input$secPause
    else
      secPause <<- 60*60
    return(secPause)
  })
  
  output$distPlot <- renderPlot( {
    dist <- rnorm(input$obs)
    if(updateTracker() <= 5) {
      # generate an rnorm distribution and plot it
      hist(dist, main = paste("Histogram count =" , updateTracker() )
           )
    }
    else {
      updates <<- 0
      hist(dist, main = paste("Last Histogram count =", 
                              as.numeric(updater(updates)), "with secPause =", 
                              as.numeric(autoControl()))
           )
    }
  })

})

ui.R

library(shiny)

# Define UI for application that plots random distributions 
shinyUI(pageWithSidebar(
  
  headerPanel("Hello Shiny!"),
    sidebarPanel(
      sliderInput("obs", 
                  "Number of observations:", 
                  min = 1,
                  max = 1000, 
                  value = 50)
      ,
      
      selectInput(inputId = "secPause",
                  label = "Seconds between displays:",
                  choices = c(1, 2, 3, 60*60),
                  selected = 1)
    ),
    
    mainPanel(
      plotOutput("distPlot")
    )
  ))