simple streaming shiny plot

server.R

set.seed(42)
dat <- rnorm(1)
shinyServer(function(input, output) {  
  fetchData <- reactive(function() {
    invalidateLater(1000)
    qt <- rnorm(1)
    dat <<- c(dat, qt)
    dat
  })
  output$plot_dat <- reactivePlot(function() { plot(fetchData(), type='l') })

  # Allow user to download data from server
  output$downloadData <- downloadHandler(
    filename = function() { "streaming.csv" },
    content = function(file) {
      write.csv(dat, file)
    }
  )  
})

ui.R

shinyUI(bootstrapPage(
  div(class="container",
    plotOutput("plot_dat"),
    downloadButton('downloadData', 'Download')
  )
))