R Shiny - Reactive dataframe download to csv

Question

I have produced an app that allows the user to upload multiple csv files.

These csvs then 'rbind' together, 'read.csv' and have a column added to the df which is the filename.

The df is then processed to produce various plots which are downloadable. This works perfectly. However when I try download a specific data frame from within the reactive element I can't get it to work.

In this example I want to download df1 from within the testinput reactive function.

UI:

    dashboardPage( skin = "black",
   dashboardHeader(title = "myApp"),
   dashboardSidebar(collapsed = TRUE,
   sidebarMenu(
    menuItem("Home", tabName = "dashboard1", icon = icon("home", lib = 
  "glyphicon"))
    ) 
    ),
   dashboardBody(
     tags$head(tags$style(HTML('
      .main-header .logo {
                          font-family: "Times New Roman", serif;
                          font-weight: bold;
                          font-size: 24px;
                          }
                          '))),

tabItems(
  tabItem(tabName = "dashboard1",
          fileInput("file1",
                    label="Input files:",
                    multiple = TRUE),
          downloadButton('downloadData', 'Download Data')
  )
  )

)
)

Server:

     library(shiny)
     library(shinydashboard)

     #server start
     function(input, output) {

       testinput<- reactive({
if(is.null(input$file1))
  return ()
else 
{
  nfiles = nrow(input$file1) 
  csv = list()
  for (i in 1 : nfiles)
  {

    csv[[i]] = read.csv(input$file1$datapath[i])

  }

  csv_names <- input$file1[['name']]
    actual_names<-input$statics$name
  df1<-cbind(actual_names, csv_names)
  mydata <- do.call(rbind, lapply(csv_names, function(x) cbind(read.csv(x), name=strsplit(x,'\\.')[[1]][1])))
    df1<-cbind(df1, mydata)    
  }
   })

     output$downloadData <- downloadHandler(
filename = function() { paste(input$downloadData, " ",Sys.Date(),".csv",sep="") },
content = function(file) {
  write.csv(df1,file)
}
    )

 )


   }

Any help would be great as I have searched lots of SO and other forums and I'm pretty stuck.

Answer 1

@Chabo was correct:

I had to create a new reactive() and then render as an output$ to my UI.

I could then download reactive event

Answer 2

I think you can return the variable you wish to download in the reactive function and then add a downloaddata in the server function like this:

library(shiny)
library(shinydashboard)

#server start
function(input, output) {

  testinput<- reactive({
    if(is.null(input$file1)){
        return ()
    }
    else{
        nfiles = nrow(input$file1) 
        csv = list()
    }

    for (i in 1 : nfiles){

        csv[[i]] = read.csv(input$file1$datapath[i])

    }

    csv_names <- input$file1[['name']]
    actual_names<-input$statics$name
    df1<-cbind(actual_names, csv_names)
    mydata <- do.call(rbind, lapply(csv_names, function(x) cbind(read.csv(x), name=strsplit(x,'\\.')[[1]][1])))
    df1<-cbind(df1, mydata)  
    return(df1)
  })

  output$downloadData <- downloadHandler(
    filename = function() {
      paste(input$dataset, ".csv", sep = "")
    },
    content = function(file) {
      write.csv(testinput(), file, row.names = FALSE)
    })
}