如何使用上传文件中的 DT 和 Shiny 编辑表格？

Question

我依靠找到here 的代码块来创建一个闪亮的应用程序来上传表格，编辑表格，然后下载表格。我已经设法编辑了一个已经加载到内存（iris）中的表格，但是如何编辑要在 Shiny 中上传的表格？。

我已经尝试了上面链接中的代码并验证它可以工作。我也尝试了下面的代码，这也有效。我无法实现的是将数据框x 转换为分配给上传文件的反应对象，并相应地编辑对x 的所有引用。

# This code works, but lacks a fileinput object 
# and needs to be amended for a reactive dataframe...
library(shiny)
library(DT)
shinyApp(
  ui = fluidPage(
    fluidRow(
    # ~~ add fileInput("file1", "Choose file") here ~~
    downloadButton("download")
    ),
    fluidRow(
    DT::dataTableOutput('x1')
    )
  ),
  server = function(input, output, session) {
    # Do I make x reactive?
    x = iris
    x$Date = Sys.time() + seq_len(nrow(x))
    output$x1 = DT::renderDataTable(x, selection = 'none', rownames = FALSE, edit = TRUE)

    proxy = dataTableProxy('x1')

    observeEvent(input$x1_cell_edit, {
      info = input$x1_cell_edit
      str(info)
      i = info$row
      j = info$col + 1
      v = info$value
      x[i, j] <<- DT:::coerceValue(v, x[i, j])
      replaceData(proxy, x, resetPaging = FALSE, rownames = FALSE)
    })

    output$download <- downloadHandler("example.csv", 
                                       content = function(file){
                                         write.csv(x, file)
                                       },
                                       contentType = "text/csv")

    }
)

之前的尝试都抛出了错误，主要是因为没有活动的反应上下文就不允许操作。

下面的代码显示了我想要实现的目标，但会引发错误： “缺少参数“expr”，没有默认值”

library(shiny)
library(DT)
shinyApp(
  ui = fluidPage(
    fluidRow(
      fileInput("upload", "Choose CSV File",
                multiple = FALSE,
                accept = c("text/csv",
                           "text/comma-separated-values,text/plain",
                           ".csv")),
    downloadButton("download")
    ),
    fluidRow(
    DT::dataTableOutput('x1')
    )
  ),
  server = function(input, output, session) {
    #x = iris

    # In this edited example x is now a reactive expression, dependent on input$upload
    x <- eventReactive({


      # input$file1 will be NULL initially. After the user selects
      # and uploads a file, head of that data file by default,
      # or all rows if selected, will be shown.

     req(input$upload)

      # when reading semicolon separated files,
      # having a comma separator causes `read.csv` to error
      tryCatch(
        {
          x <- read.csv(input$upload$datapath,
                         header = TRUE,
                         sep = ",",
                         stringsAsFactors = TRUE,
                         row.names = NULL)

        },
        error = function(e) {
          # return a safeError if a parsing error occurs
          stop(safeError(e))
         }
      )
    })

    #x$Date = Sys.time() + seq_len(nrow(x))
    output$x1 = DT::renderDataTable(x(), selection = 'none', rownames = FALSE, edit = TRUE)

    proxy = dataTableProxy('x1')

    observeEvent(input$x1_cell_edit, {
      info = input$x1_cell_edit
      str(info)
      i = info$row
      j = info$col + 1
      v = info$value
      x()[[i, j]] <<- DT:::coerceValue(v, x()[[i, j]])
      newdf <- x()
      replaceData(proxy, newdf, resetPaging = FALSE, rownames = FALSE)
    })

    output$download <- downloadHandler("example.csv", 
                                       content = function(file){
                                         write.csv(x(), file)
                                       },
                                       contentType = "text/csv")

    }
)

Answer 1

感谢 Stephane，以及来自 this related question 的灵感，我想我有了答案。

关键是使用 reactiveValues 作为 DT:::coerceValue 不喜欢反应式表达式的解决方法。我已经包含了一个逐字文本输出来说明在编辑数据表后对表的存储更改。下载按钮也允许您下载已编辑的表格。

library(shiny)
library(DT)
shinyApp(
  ui = fluidPage(
    fluidRow(
      fileInput("upload", "Choose CSV File",
                multiple = FALSE,
                accept = c("text/csv",
                           "text/comma-separated-values,text/plain",
                           ".csv")),
    downloadButton("download")
    ),
    fluidRow(
    DT::dataTableOutput('x1'),
    verbatimTextOutput("print")
    )
  ),
  server = function(input, output, session) {

    # In this edited example x is now a reactive expression, dependent on input$upload

    # Key to the solution is the use of reactiveValues, stored as vals
    vals <- reactiveValues(x = NULL)

    observe({


      # input$upload will be NULL initially. After the user selects
      # and uploads a file, head of that data file by default,
      # or all rows if selected, will be shown.

     req(input$upload)

      # when reading semicolon separated files,
      # having a comma separator causes `read.csv` to error
      tryCatch(
        {
          x <- read.csv(input$upload$datapath,
                         header = TRUE,
                         sep = ",",
                         stringsAsFactors = TRUE,
                         row.names = NULL)

        },
        error = function(e) {
          # return a safeError if a parsing error occurs
          stop(safeError(e))
         }
      )
      # Reactive values updated from x
      vals$x <- x
    })

    output$print <- renderPrint({
      vals$x
    })
    output$x1 = DT::renderDataTable(vals$x, selection = 'none', rownames = FALSE, edit = TRUE)

    proxy = dataTableProxy('x1')

    observeEvent(input$x1_cell_edit, {
      info = input$x1_cell_edit
      str(info)
      i = info$row
      j = info$col + 1
      v = info$value
      # Below is the crucial spot where the reactive value is used where a reactive expression cannot be used
      vals$x[i, j] <<- DT:::coerceValue(v, vals$x[i, j])
      replaceData(proxy, vals$x, resetPaging = FALSE, rownames = FALSE)
    })

    output$download <- downloadHandler("example.csv", 
                                       content = function(file){
                                         write.csv(vals$x, file, row.names = F)
                                       },
                                       contentType = "text/csv")

    }
)

Answer 2

见?eventReactive。

你应该这样做：

x <- eventReactive(input$upload, { # 'input$upload' was the "expr missing"
       ......

或

x <- reactive({
        req(input$upload)
        ......