R Shiny - Download plot demo

server.r

library(shiny)
shinyServer(function(input,output)({
  # x contains all the observations of the x variable selected by the user. X is a reactive function
  x <- reactive({
    iris[,as.numeric(input$var1)]
  })
  # x contains all the observations of the y variable selected by the user. Y is a reactive function
  y <- reactive({
    iris[,as.numeric(input$var2)]
    
  })
  # xl contains the x variable or column name of the iris dataset selected by the user
  xl <- reactive({
    names(iris[as.numeric(input$var1)])
    })
  # yl contains the y variable or column name of the iris dataset selected by the user
  yl <- reactive({
    names(iris[as.numeric(input$var2)])
  })
  
  # render the plot so could be used to display the plot in the mainPanel
  output$plot <- renderPlot({
    plot(x=x(), y=y(), main = "iris dataset plot", xlab = xl(), ylab = yl())
    
  })
  
  # downloadHandler contains 2 arguments as functions, namely filename, content
  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
      plot(x=x(), y=y(), main = "iris dataset plot", xlab = xl(), ylab = yl()) # draw the plot
      dev.off()  # turn the device off
    
    } 
)
  
  
  
}))

ui.r

library(shiny)
shinyUI(fluidPage(
  titlePanel("Download base plot in Shiny - an example"),
  sidebarLayout(
   sidebarPanel(
      selectInput(inputId = "var1", label = "Select the X variable", choices = c("Sepal.Length" = 1, "Sepal.Width" = 2, "Petal.Length" = 3, "Petal.Width" = 4)),
      selectInput(inputId = "var2", label = "Select the Y variable", choices = c("Sepal.Length" = 1, "Sepal.Width" = 2, "Petal.Length" = 3, "Petal.Width" = 4), selected = 2),
      radioButtons(inputId = "var3", label = "Select the file type", choices = list("png", "pdf"))
),
    mainPanel(
      plotOutput("plot"),
      downloadButton(outputId = "down", label = "Download the plot")
      )
    )
  
  ))

Rather than draw your plot twice, once in the renderPlot() and again in the downloadHandler(), you can create a plot function and call that in both instances.

e.g.

## a plot function
myPlot <- function(){
    plot(x=x(), y=y(), main = "iris dataset plot", xlab = xl(), ylab = yl())
}

## call the plot function to show on the page
output$plot <- renderPlot({
    myPlot()
})

## call the plot function when downloading the image
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
      myPlot() 
      dev.off()  # turn the device off

    } 
)

Hi. downloadHandler returns a blank image when the plot is saved in a reactive element. Any idea why?

I couldn't download as a pdf file somting could help me

Plot

implied by the dependency graph.

Gage_RR_plot <- reactive({
if(is.null(csv_table())){return()}

ss.rr(var = Voltage, part = Battery,
               appr = Voltmeter,
               data = csv_table(),
               main = "Six Sigma Gage R&R Measure",
               sub = "Batteries Project MSA")

 })

output$Gageplot <- renderPlot({
print(Gage_RR_plot())
})

the following renderUI is used to dynamically generate the tabsets when the file is loaded. Until the file is loaded, app will not show the tabset.

output$contents <- renderUI({
if(is.null(csv_table()))
h5("N/D")
else
tabsetPanel(tabPanel("Data", tableOutput("table")),
tabPanel("Output Gage R&R",renderPrint(
#Gage R&R
ss.rr(var = Voltage, part = Battery,
appr = Voltmeter,
data = csv_table(),
main = "Six Sigma Gage R&R Measure",
sub = "Batteries Project MSA"))),
tabPanel("Gage R&R", plotOutput("Gageplot",height = 700 ,width = 500),
# downloadHandler contains 2 arguments as functions, namely filename, content

                     output$downloadPlot <- downloadHandler(filename = function(){
                       paste("","pdf",sep=".")
                     },
                       #specify file name                             
                         content = function(file) {
                        #open de device
                           pdf(file)
                           #create the plot
                          print(Gageplot()) 
                          # close the device
                           dev.off()
                        },
                 contentType='pdf'
                       
                     )))

})

})

shinyApp(ui, server)