Demo of problem with renderUI and animation slider

server.R

library(shiny)

grp <- c(rep("A", 900), rep("B", 1200))

# Define server logic for slider examples
shinyServer(function(input, output) {
  
  sub <- reactive({
    grp[grp %in% input$group]
  })
  
  output$animationControl <- renderUI({
    s <- length(sub())
    sliderInput(inputId = "animation",
                label = "renderUI animation", 
                min = 1, 
                max = s,
                value = 1,
                step = 1, 
                animate=animationOptions(interval=300, loop=F)
    )
  }) 
  
  # Reactive expression to compose a data frame containing all of the values
  sliderValues <- reactive({
    if (is.null(input$animation)){return(NULL)}
    # Compose data frame
    data.frame(
      Name = c("Integer", 
               "Decimal",
               "Range",
               "Custom Format",
               "Animation"),
      Value = as.character(c(input$integer, 
                             input$decimal,
                             paste(input$range, collapse=' '),
                             input$format,
                             input$animation)), 
      stringsAsFactors=FALSE)
  }) 
  
  # Show the values using an HTML table
  output$values <- renderTable({
    sliderValues()
  })
})

ui.R

library(shiny)

# Define UI for slider demo application
shinyUI(pageWithSidebar(
  
  #  Application title
  headerPanel("Sliders"),
  
  # Sidebar with sliders that demonstrate various available options
  sidebarPanel(
    # Simple integer interval
    sliderInput("integer", "Integer:", 
                min=0, max=1000, value=500),
    
    # Decimal interval with step value
    sliderInput("decimal", "Decimal:", 
                min = 0, max = 1, value = 0.5, step= 0.1),
   
    # Specification of range within an interval
    sliderInput("range", "Range:",
                min = 1, max = 1000, value = c(200,500)),
    
    # Provide a custom currency format for value display, with basic animation
    sliderInput("format", "Custom Format:", 
                min = 0, max = 10000, value = 0, step = 2500,
                format="$#,##0", locale="us", animate=TRUE),
    
    # Animation with custom interval (in ms) to control speed, plus looping
#     sliderInput("animation", "Looping Animation:", 1, 2100, 1, step = 10, 
#                 animate=animationOptions(interval=300, loop=FALSE)),
    
    wellPanel(
      checkboxGroupInput("group", "Group",
                         list("A", "B"),
                         selected = c("A", "B")
      ),
      uiOutput("animationControl")
    )
  ),
  
  # Show a table summarizing the values entered
  mainPanel(
    tableOutput("values")
  )
))