Q:

Shiny: Error in plot.window: need finite 'xlim' values on page load

I am trying to create a barplot in R shiny. Data are coming from a csv file and they are filtered according to user's selection in selectInput and sliderInput controls.
When the page is loading I am getting the error: 

Error in plot.window: need finite 'xlim' values.

Then, when the page is fully loaded, all is fine and working. 
It looks like the first time app runs, popData which I pass to function barplot is null. I was trying to check if popData is null as advised here before rendering plot but still getting the same error. When I use hard-coded values for selectedCountry and selectedYear instead of reactive expressions, it works okay, I do not get this initial error what makes me think results of selectInput  and sliderInput may not available yet when plot is rendered first time(?)
How can I fix this? Thanks.
ui <- fluidPage(
  titlePanel(title = h3("Population by age")),
  sidebarLayout(
    sidebarPanel(
      uiOutput("geoSelector"),
      br(),
      uiOutput("yearSlider"),
      br()
    ),
    mainPanel(
      plotOutput("barChart"),
      br()
    ))
)

server <- function(input, output) {

  data <- read.csv("data.csv")

  geo = sort(unique(data[,"GeographyName"]))
  output$geoSelector <- renderUI({
    selectInput("country", "Select country", as.list(geo)) 
  })

  minY <- min(unique(data[,"PeriodValue"]))
  maxY <- max(unique(data[,"PeriodValue"]))
  output$yearSlider <- renderUI({
    sliderInput("year", "Select year", min=minY, max=maxY, 
                value=as.integer(format(Sys.Date(), "%Y")), sep="", animate = TRUE, step=1)
  })
  selectedCountry <- reactive({input$country}) 
  selectedYear <- reactive({input$year})

  selectedData <- reactive({subset(data, GeographyName == selectedCountry() & 
                           PeriodValue == selectedYear())})
  selectedDataSorted <- reactive({selectedData()[order(selectedData()$AgeCategoryId),c(1:8)]})
  popData <- reactive({selectedDataSorted()$DataPoint})
  categ <- reactive({selectedDataSorted()$AgeCategory})

  output$barChart <- renderPlot({
    barplot(popData(),names.arg=categ(), cex.names = 0.7, border=NA,
            xlab="Age Category", ylab="Population (m)")
  })
}

shinyApp(ui = ui, server = server)

A:

Does this solve your issue?
 output$barChart <- renderPlot({
    validate(need(nrow(popData())>0, "Please select a data set"))
    barplot(popData(),names.arg=categ(), cex.names = 0.7, border=NA,
            xlab="Age Category", ylab="Population (m)")
  })

