闪亮：从反应变量中删除列

Question

我想使用 shiny 读取 CSV 文件，然后允许用户删除选定的列。

下面是我的例子。但我一直收到 no applicable method for 'select' applied to an object of class "c('reactiveExpr', 'reactive', 'function')" 错误。

删除功能已经在反应环境中，我不知道如何解决这个问题。

非常感谢您的帮助。

library(shiny)

ui = fluidPage(
  fileInput(inputId = "rawFile", label="File"), 
  uiOutput("selectColumn"),
  actionButton(inputId = "Remove", label = "Remove"),
  tableOutput("DFTable")
)

server = function(input, output, session){
  # initiate a reactive value
  df <- reactiveValues(data = NULL)
  removecolumn <- function(df, nameofthecolumn){dplyr::select(df, -nameofthecolumn)}
  
  inputData <- reactive({
    inFile <- input$rawFile
    if (is.null(inFile)){return(NULL)}
    read.csv(inFile$datapath, header = T)
  })
  
  # update column names
  output$selectColumn <- renderUI({
    shiny::req(inputData())
    selectInput(inputId = "selectColumn",
                label = "Remove selected sample(s)",
                multiple = TRUE,
                choices = names(inputData())
                )
  })
  
  df$data <- reactive({inputData()})
  
  # delete column
  observeEvent(input$Remove, {
    df$data <- removecolumn(df$data, input$selectColumn)
  })
  
  # show result
  output$DFTable <- renderTable(df$data())
  
}

shinyApp(ui, server)

Answer 1

而不是分配给 df$data（即 df$data<-reactive(inputData())），您可以在反应中分配以读取原始数据，如下所示：

  inputData <- reactive({
    inFile <- input$rawFile
    if (is.null(inFile)){return(NULL)}
    data = read.csv(inFile$datapath, header = T)
    df$data = data
    return(data)
  })

然后，我们观察 input$Remove，然后像这样更新 df$data：

  observeEvent(input$Remove, {
      df$data <- removecolumn(df$data, input$selectColumn)
  })

完整代码：

library(shiny)

ui = fluidPage(
  fileInput(inputId = "rawFile", label="File"), 
  uiOutput("selectColumn"),
  actionButton(inputId = "Remove", label = "Remove"),
  tableOutput("DFTable")
)

server = function(input, output, session){
  # initiate a reactive value
  df <- reactiveValues(data = NULL)
  removecolumn <- function(df, nameofthecolumn){dplyr::select(df, -(all_of(nameofthecolumn)))}
  
  inputData <- reactive({
    inFile <- input$rawFile
    if (is.null(inFile)){return(NULL)}
    data = read.csv(inFile$datapath, header = T)
    df$data = data
    return(data)
  })
  
  # update column names
  output$selectColumn <- renderUI({
    shiny::req(inputData())
    selectInput(inputId = "selectColumn",
                label = "Remove selected sample(s)",
                multiple = TRUE,
                choices = names(inputData())
    )
  })
  
  ##df$data = reactive(inputData())
  
  observeEvent(input$Remove, {
      df$data <- removecolumn(df$data, input$selectColumn)
  })
  
  # show result
  output$DFTable <- renderTable({
    df$data
  })
  
}

shinyApp(ui, server)

闪亮：从反应变量中删除列

Shiny: delete columns from a reactive variable

shiny

reactive