r - Shiny app: downloadHandler does not produce a file

Question

I can't figure out what's going on - everything seems to work but my app does not generate a file - although it looks like it does. I run it in Windows, on RStudio 0.98.125, and I run it using the line: runApp() Below is a very simple reproducible example:

my 'ui.R':

shinyUI(pageWithSidebar(

  headerPanel("My App"),

  sidebarPanel(
    numericInput('NumRuns','Number of runs',value=3,min=3,max=10,step=1),

    actionButton(inputId="goButton","Run!"),

    textInput("downloadData","Save My Data Frame:",value="Data Frame 1"),
    downloadButton('downloadData','Save my file!')

  ),

  mainPanel(
    tabPanel("Some Text",
             h4(textOutput("caption2")),
             tableOutput("mydf"),
             value=3))
  ))

my 'server.R':

shinyServer(function(input,output){

  # Creating files for download at the end

  myout = reactive({
    if(input$goButton==0) return(NULL)

      nrruns=input$NumRuns
      mylist=NULL
      for(i in 1:nrruns){
        mylist[[i]]<-data.frame(a=rnorm(10),b=runif(10))
        names(mylist)[i]<-paste("dataframe",i,sep="")
      }
      return(mylist)
  })

     output$mydf <- renderTable({
     if(input$goButton==0) return(NULL)
     input$goButton
     isolate(
       myout()$dataframe1
     )
   })

  output$downloadData <- downloadHandler(
    filename = function() { paste(input$downloadData, " ",Sys.Date(),".csv",sep="") },
    content = function(file) {
      write.csv(myout()$dataframe1,file,row.names=F)
    }
  )

})

Answer 1

Note the download button does not work in the RStudio viewer. Your friend might be using the RStudio viewer to view the app. If that is the case, please open the app in the external web browser (there is a drop-down list on the right of the "Run App" button: Run in Window, Run in Viewer Pane, Run External; choose the last one).