Order of two renderPlot() in Shiny

Question

On a Shiny page I notice that on a given tabPanel, plots for all renderPlot() statements are displayed simultaneously rather than one after another. Even when I add Sys.sleep(n) in between these renderPlot ... it simply deplays the rendering, but the renderPlot() outputs are not displayed in the order of their execution. I would like them to display one after another and provide user progress bar to indicate which plot is being plotted. Thanks.

Answer 1

UI

tabPanel 
        (
            sidebarLayout
            (
                sidebarPanel
                (
                    fileInput('dataSource', 'Upload Data',accept = c('text/csv','text/comma-separated-values','text/tab-separated-values','text/plain','.csv','.tsv'),multiple=TRUE)
                ),
                mainPanel
                (
                    fluidRow(column(width = 3, style = "background-color: transparent;", class = "well",plotOutput("comp1", height = 300,width = 300)),
                    column(width = 3, style = "background-color: transparent;", class = "well",plotOutput("comp2", height = 300,width = 300))),
                    tags$hr()
                )
            )
        )

Server

values <- reactiveValues(df_data = NULL)
    observeEvent(input$dataSource, { values$df_data <- read.csv(input$dataSource$datapath)})    

    Comp1 <- reactive({
    plComp1 <- eqComp1(values$df_data [-(1:2)]))))
    })
    Comp2 <- reactive({
    plComp2 <- eqComp2(values$df_data [-(1:2)]))))
    })

    output$comp1 <- renderPlot({
    withProgress(message = 'Plotting in progress ...', value = 0, {
       for (i in 1:15) {
         incProgress(1/15)
         Sys.sleep(0.5)
       }    
    plot( values@df_data[,1], Comp1())

    })
    })
    output$comp2 <- renderPlot({
    withProgress(message = 'Plotting in progress ...', value = 0, {
       for (i in 1:15) {
         incProgress(1/15)
         Sys.sleep(0.5)
       }    
    plot( values@df_data[,1], Comp2())

    })
    })