downloading file in shiny

Question

I want a user to download a file which is in tabular format with header along with two search widgets on top. The output is forecasted values along with 80%(High-low) and 95%(High-low) confidence interval.So there are five columns, five rows(default). However, i am having two challenges here.

Challenge 1: When I run the app, after clicking on "Download the file" filename is coming as download data with no extension whereas I have mentioned filename should be "forecasted" with png extension and it should come as forecated.png

Challenge 2: After typing png as extension while saving the file, the file is saved but nothing gets printed.

I have searched in various forums and try to replicate them but nothing seems to be working.

Please suggest.

shiny UI

library(shiny)    
downloadButton(outputId = "downloaddata" ,label ="Download the file"),

shiny server

output$downloaddata<-downloadHandler(

    filename = function(){
      paste("forecasted","png",sep=",")
    },
    content = function(file){
      png(file)
      h <-input$fst
      tab<-forecast(Model_mape(),h) 
      datatable(as.data.frame(tab), options = list(
         columnDefs = list(list(targets = c(1, 3), searchable = FALSE)),
         pageLength = 10))
      dev.off()

    }

  )

Answer 1

Maybe it could help you (it's a simple instance):

Ui :

library(shiny)

shinyUI(fluidPage(

  mainPanel(plotOutput("plot1"),
           downloadButton("downloadplot","Download your plot"))

  ))

Server :

library(shiny)

shinyServer(function(input, output) {
  your_plot = function(){
    (plot(rnorm(1000,0,1)))
  }


  output$plot1 <- renderPlot({
    your_plot()
  })

  output$downloadplot <- downloadHandler(
    filename = "plot_exemple.png",
    content = function(file) {
      png(file, width = 1200, height = 800)
      print(your_plot())
      dev.off()
    })

  })

With this, you can easily download a png (open it in a browser).