如何在R Shiny中通过按钮触发拆分选择菜单选中的列

• 事件绑定错误：拆分逻辑的observeEvent监听对象是下拉框选择事件input$selectcolumn，只要下拉选项变更就会触发拆分，没有绑定到「SplitColumn」按钮的点击事件input$Splitcolumn
• 下拉框配置错误：selectInput的choices参数错误写为c('ID, Type')，仅生成单个字符串选项，无法正常选择ID、Type两个独立列。另外硬编码列名兼容性差，建议上传文件后动态匹配实际列名
• 依赖包缺失：splitColumn函数用到reshape2包的colsplit方法，代码中未声明加载会触发隐式报错
• 文件读取配置错误：测试数据为空格分隔，默认read.csv按逗号分隔读取，会导致列识别错误

SplitColumn.R #

library(reshape2)
splitColumn <- function(data, column_name) {
  newColNames <- c("Unmerged_type1", "Unmerged_type2")
  newCols <- colsplit(data[[column_name]], " ", newColNames)
  after_merge <- cbind(data, newCols)
  after_merge[[column_name]] <- NULL
  after_merge
}

app.R #

library(shiny)
source('SplitColumn.R')

ui <- fluidPage(
  sidebarLayout(
    sidebarPanel(
      fileInput("file1", "Choose CSV File", accept = ".csv"),
      checkboxInput("header", "Header", TRUE),
      actionButton("Splitcolumn", "SplitColumn"),
      # 初始下拉选项为空，上传文件后动态更新
      selectInput(inputId='selectcolumn', label='select column', choices = NULL)
    ),
    mainPanel(
      tableOutput("contents")
    )
  )
)

server <- function(input, output, session) {
  rv <- reactiveValues(data = NULL)
  
  # 上传文件后读取数据，同时更新下拉框的列选项
  observe({
    file <- input$file1
    ext <- tools::file_ext(file$datapath)
    
    req(file)
    validate(need(ext == "csv", "Please upload a csv file"))
    
    # 加sep=""适配空格分隔的测试数据
    rv$data <- read.csv(file$datapath, header = input$header, sep = "")
    # 动态更新下拉选项为文件实际列名
    updateSelectInput(session, "selectcolumn", choices = colnames(rv$data))
  })
  
  output$contents <- renderTable({
    req(rv$data)
    rv$data
  })
  
  # 绑定拆分逻辑到按钮点击事件，仅点击按钮才执行拆分
  observeEvent(input$Splitcolumn, {
    req(rv$data, input$selectcolumn)
    rv$data <- splitColumn(rv$data, input$selectcolumn)
  })
}
shinyApp(ui, server)

内容的提问来源于stack exchange，提问作者Kevin Tracey