Working with a reactive() dataframe inside eventReactive()?

Question

I was hoping someone could provide some guidance on resolving an issue I have. For background, I\'m trying to create an interface for users to upload a csv of news stories, whic

Answer 1

I think you should made several changes to make your reactive and the output works.

• remove the return in the expression of reactive because reactive only captures the last output from the expression.
• Move all the reactive outside of any function because you can always check if the input$goButton (in your case) is triggered inside reactive function.
• Use ObserveEvent for the triggering of events (like input$goButton) instead of eventReactive because eventReactive only gives out a value (rather than renders for outputs and keeps them in the scope).
• Use reactiveValues for any variable (df_sheet) that changes values in ObserveEvent
• Change df to df_sheet

Here is the modified server function:

server <- function(input, output){
  v <- reactiveValues(df_sheet = NULL)

  sheet <- reactive({
    infile <- input$datafile
    if (is.null(infile)) {
      # User has not uploaded a file yet
      NULL
    } else {
      tbl = read.csv(infile$datapath, stringsAsFactors = FALSE)

      if(!is.null(selected_row_id())) {
        if (selected_row_id() > 0){  
          tbl[selected_row_id(),1] <- input$truefalse
        }
      } 

      tbl
    }
  })


  # selected row ID from data table
  selected_row_id <- reactive({
    input$sheet_rows_selected
  })


  # reactive dataframe object
  observeEvent(input$goButton, {

    v$df_sheet <- sheet()

    # selectable data table 
    output$sheet <- renderDataTable({
      v$df_sheet
    }, selection = "single")

  }, ignoreNULL = FALSE)


  # Save when click the button
  observeEvent(input$save, {

    # text of article
    output$text<-renderText({v$df_sheet[input$sheet_rows_selected, "lede"]})

    # download button
    output$download_data <- downloadHandler(
      filename = "updated_data.csv",
      content = function(file) {
        write.csv(v$df_sheet, file, row.names = FALSE)
      }
    )

    write.csv(v$df_sheet, input$save_file, row.names = FALSE)
  })

}

Answer 2

I managed to get this working by storing the data in a reactiveValues, replacing eventReactive() with observeEvent, then updating the data using isolate().

Working server code

server <- function(input, output){
  v = reactiveValues(df_sheet = NULL)
  sheet <- reactive({
    infile <- input$datafile
    if (is.null(infile)) {
      # User has not uploaded a file yet
      return(NULL)
    }
    tbl = read.csv(infile$datapath, stringsAsFactors = FALSE)
    v$df_sheet = tbl
    tbl
  })



  # reactive dataframe object
   observeEvent(input$goButton, {
     isolate({
       if(!is.null(selected_row_id())) {
         if (selected_row_id() > 0){  
           v$df_sheet[selected_row_id(),1] <- input$truefalse
         }
       } 
    })
  }, ignoreNULL = FALSE)

  # selectable data table 
  output$sheet <- renderDataTable({
    v$df_sheet[,c(1,2)]
  }, selection = "single")

  # selected row ID from data table
  selected_row_id <- reactive({
    input$sheet_rows_selected
  })

  # text of article
  output$text<-renderText({sheet()[input$sheet_rows_selected, "lede"]})

  # Save when click the button
  observeEvent(input$save, {
    write.csv(v$df_sheet, paste('data/',input$save_file, sep=''), row.names = FALSE)
  })

  # download button
  output$download_data <- downloadHandler(
    filename = "updated_data.csv",
    content = function(file) {
      write.csv(v$df_sheet, paste('data/', file, sep=''), row.names = FALSE)
    }
  )

}

shinyApp(ui = ui, server = server)