Shiny app with leaflet: uiOutput not showing up until goButton is pressed

Question

I'm working on a Shiny app where a leaflet map animates through time, but you can pause it and then use a slider to look at specific years. I've made a dummy version of the functionality and posted it here: https://seth127.shinyapps.io/slider

My issue is, the sliderInput to pick the year (which is inside renderUI in the server.R) doesn't appear until you've first clicked the goButton (which pauses the animation). I can't seem to figure out why.

I want it to default to year 2000 (when input$animate==0). I added a text input to verify that this functionality should work, and it works for the renderText, but not the renderUI. Any help is much appreciated. Code is below:

server.R

require(maps)
require(leaflet)
require(shiny)

fakeData <- data.frame(year=seq(1974,2014,by=1), 
                   lat=seq(34, 40, by=0.1463415),
                   long=seq(-118,-73, by=1.097561),
                   artist="fake",
                   album="fake",
                   hometown="fake",
                   chart="PJ")

pickYear <- function(year, data) {
    yearCities <- data[as.numeric(data$year)==year, ]
    yearCities
}

shinyServer(
function(input, output) {
    #refresh animation every 60 seconds
     getit <- reactive({
        invalidateLater(60000, session=NULL)
        Sys.time()
    })
    #change animation year every 2 seconds
    year <- reactive({
        if(input$animate %% 2 != 0) {
            invalidateLater(2000, session=NULL)
            1984 + (round(as.numeric(Sys.time() - getit())/2))
        } else {1984 + (round(as.numeric(Sys.time() - getit())/2))}

        })


output$pressedGo <- reactive({if(input$animate==0) {"you haven't pressed go"} else {"now you have"}})

output$reactiveSlider <- renderUI({
    yearVal <- if(input$animate == 0) {2000} else {year()}
    sliderInput('year', label='Pick A Year:', value = yearVal,
                min = 1984, max = 2015, step = 1, sep="")

})

    output$map <- renderLeaflet({
            leaflet(data = pickYear(input$year, fakeData)) %>% addTiles() %>%
                addMarkers(~long, ~lat) %>% setView(-97.887318, 40.422487, 4) 
})

})

ui.R

require(maps)
require(leaflet)
require(shiny)

shinyUI(
pageWithSidebar(
    # Application title
    headerPanel(
        ""
    ),
    sidebarPanel(

    ),
    mainPanel(
        uiOutput("reactiveSlider"),
        actionButton('animate', "Animate/Pause Map"),
        h3(textOutput("pressedGo")),
        p(" "),
        leafletOutput("map")
    )
  )
)

pretty strange, seems there is some naming conflict. If you rename reactiveSlider to something that doesnt start with 'r', it works. — Rorschach

Chris Chris · Accepted Answer · 2015-11-11T15:13:02

Not an explanation of the issue, but a potential alternative - you can use the native functionality in shiny to do what you want:

sliderInput("animation", "Looping Animation:", 1984, 2015, 1, step = 1, 
                animate=animationOptions(interval=1, loop=T))

The key line here is the animation argument. See more examples here: http://shiny.rstudio.com/articles/sliders.html

Shiny app with leaflet: uiOutput not showing up until goButton is pressed

1 Answers