Automating Interaction with R Shiny App - Revised

counterAutoDemo-6.R

library(shiny)

longPause <- 10
updates <- 0
updater <- function(){ updates + 1 }

runApp(list(
  ui = 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),
    	selected = 2)
  ),

  mainPanel(
    plotOutput("distPlot")
  )
),

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

This is a revision to code presented in the following StackOverflow question:
http://stackoverflow.com/questions/18622100/automating-interaction-with-r-shiny-app

Ram’s suggestion helped me get past the error display and make some more, minor changes. The last part of the objective remains undone -- for “new user input to restart it.” The automated cycle of 5 displays should restart when either UI input (obs or secPause) is changed. However, only 1 histogram is shown each time obs is changed, and the short pause of the reactive source input$secPause stays inactive. Any suggestions please?