CODEWITHSUNDEEP
rshiny
David
David

Reputation: 524

Why the function downloadHandler doesnot download the file in Rshiny?

My ur.R file goes as follows:

library(shiny)


shinyUI(
  fluidPage(
    titlePanel(title = h4('Demonstraion of renderplot', align='center')),
    sidebarLayout(
      sidebarPanel(
        selectInput('var', "Select the Variable", choices = c('Sepal.Length' =1 , 'sepal width' = 2, 'Petal Length' = 3 , 'Petal Width' = 4), selected = 1),
        br(),
        sliderInput('bins', 'Select the number of bins', min = 5, max = 25, value = 15),
        br(),
        radioButtons('color', 'Color of the bins', choices = c('Green', 'Red', 'Blue'), selected = 'Green'),
        br(),
        radioButtons('type', 'Choose the type', choices = list('png', 'pdf'), selected = 'png')

      ),
    mainPanel(
      plotOutput("myhist"),
      downloadButton('down', 'Download the Plot')


    )
    )
  )
)

and my server.R goes as follows:

library(shiny)

shinyServer(function(input, output){

  colm = reactive({
    as.numeric(input$var)
  }) 
  output$myhist = renderPlot(
    {
      hist(iris[,colm()], breaks = seq(0,max(iris[,colm()], l= input$bins+1)),col =input$color, main ="Histogram of irish dataset", xlab = names(iris[colm()]))
    }
  )

  output$down <- downloadHandler(
    filename =  function() {
      paste("iris", input$var3, sep=".")
    },
    # content is a function with argument file. content writes the plot to the device
    content = function(file) {
      if(input$var3 == "png")
        png(file) # open the png device
      else
        pdf(file) # open the pdf device
      hist(colm()) # draw the plot
      dev.off()  # turn the device off

    } 
  )



})

image

When I hit the download button, It shows like the following whereas the file name suppose to be iris.png. Why this behaviour? image

I have also tried wrapping arguments of the function, downdloadHandler like this as suggested by Abinav in his comments of this video. 

output$down <- downloadHandler({
    filename =  function() {
      paste("iris", input$var3, sep=".")
    },
    # content is a function with argument file. content writes the plot to the device
    content = function(file) {
      if(input$var3 == "png")
        png(file) # open the png device
      else
        pdf(file) # open the pdf device
      hist(colm()) # draw the plot
      dev.off()  # turn the device off

    } 
  })

But this gave the error message as follows. 

Error in parse(file, keep.source = FALSE, srcfile = src, encoding = enc) : 
  G:\R_workshop_related_NITTE\Shiny\downloadPlots/server.R:17:6: unexpected ','
16:       paste("iris", input$var3, sep=".")
17:     },
         ^
Warning: Error in sourceUTF8: Error sourcing C:\Users\Mahe\AppData\Local\Temp\RtmpIPEtpl\file29805c1e4eca
Stack trace (innermost first):
    1: runApp
Error in sourceUTF8(serverR, envir = new.env(parent = globalenv())) : 
  Error sourcing C:\Users\Mahe\AppData\Local\Temp\RtmpIPEtpl\file29805c1e4eca

I am in windows machine Rstudio Version 1.1.442 with R 3.4.4.

Upvotes: 0

Views: 1180

Answers (1)

GyD
GyD

Reputation: 4072

The problem is that you don't have an input element called var3, so input$var3 returns NULL and thus the filename becomes invalid ("iris.")

You named the input type, so use input$type:

output$down <- downloadHandler(
  filename =  function() {
    paste("iris", input$type, sep=".")
  },
  # content is a function with argument file. content writes the plot to the device
  content = function(file) {
    if(input$type == "png")
      png(file) # open the png device
    else
      pdf(file) # open the pdf device
    hist(colm()) # draw the plot
    dev.off()  # turn the device off

  }
)

(Note that you're saving hist(colm()), that is not the same plot as you rendered)

When I hit the download button, It shows like the following whereas the file name suppose to be iris.png. Why this behaviour?

In RStudio Viewer:

The result from filename=function() is not used by the RStudio Viewer to save the file. This is how it was for a long time. You can download the file if you name it though and it will work.

In browsers:

The result from filename=function() works as you would expect.

Upvotes: 2

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