cleanup <- function(x){
  x <- as.character(x) # convert to character
  x <- tolower(x) # make all lowercase
  x <- trimws(x, "both") # trim white space

ui <- fluidPage(
  h2("Record Linkage Data"),
  fileInput("file1", "Upload file for cleaning", accept = c("xls", "csv"), multiple = F),
  actionButton(inputId = "clean", label = "Clean Data"),
  downloadButton("download1", "Download file1"),
  pickerInput(width = "75%",
              inputId = "pick_col1",
              label = "Select columns to display",
              choices = colnames(file1),
              selected = colnames(file1),
              options = list(
                `actions-box` = T,
                `selected-text-format` = paste("count > ", length(colnames(file1)) - 1),
                `count-selected-text` = "Alle",
                liveSearch = T,
                liveSearchPlaceholder = T

              multiple = T),

load_path <- function(path) {
    ext <- tools::file_ext(path)

    if (ext == "csv"){
      read.csv(path, header = T)
    } else if (ext == "xls" || ext == "xlsx"){
    } else{
      stop("Unknown extension: '.", ext, "'")

server <- function(input, output, session){

file1 <- reactive(load_path(input$selection$datapath[[1]]))

#file2 <- reactive(load_path(input$selection$datapath[[2]]))
  eventReactive(input$clean, {
    output$mytable <- DT::renderDataTable({
      data.frame(lapply(select(file1, input$pick_col1), cleanup))


  output$download <- downloadhandler(
    filename = function(){
      paste0(tools::file_path_sans_ext(input$filename), ".csv")


    content = function(file){
      write.csv(data(), file)


shinyApp(ui, server)

When I run the above code, I get the error : Error in is.data.frame(x) : object 'file1' not found. I am unsure why this is but I have been struggling to understand naming things in shiny. For example: I want to upload file1, then transform it. Do I continue to refer to file1 when I want to download it? These may seem like silly questions but I am asking because I don't know and I'm trying to learn. There seem to be lots of different approaches.

我想要: 1.加载文件 2.通过操作按钮,将预先指定的功能应用于选定的列 3.将转换后的数据集下载为.csv


  • 别犯贱 回复


    1. It is a very silly one (it happens to all of us). You should write downloadHandler instead of downloadhandler.
    2. The main problem: Your pickerInput is trying to select the column names of the data frame file1 when it does not exists. When you run the application the code is trying to find a file1 data frame and look its column names, but since at that time you haven't uploaded anything yet, it throws an error.
    3. On how you read files: I am not familiar with how you read files, I suggest you do something similar than what is done in this example. https://shiny.rstudio.com/gallery/file-upload.html. Note you need to use a read.* function and point the result to another name, df in the example.

    How would I solve it: 1. Set choices and selected options to NULL by default. Something like the following should work:

      pickerInput(width = "75%",
                  inputId = "pick_col1",
                  label = "Select columns to display",
                  choices = NULL,
                  selected = NULL,
                  options = list(
                    `actions-box` = T,
                    # `selected-text-format` = paste("count > ", length(colnames(file1)) - 1),
                    `count-selected-text` = "Alle",
                    liveSearch = T,
                    liveSearchPlaceholder = T
                  multiple = T)
    1. Add an updatePickerInput in the server side within an observeEvent. Something like this should work.
    observeEvent(input$file1, {
      req(input$file1) # ensure the value is available before proceeding
      df <- read.csv(input$file1$datapath)
      updatePickerInput(session = session, 
                        inputId = "pick_col1", 
                        choices = colnames(df), 
                        # ... other options) 

    如果代码还有其他问题,我的期望并不高。 我建议您从共享链接中的示例开始,并开始对其进行修改,直到获得所需的内容。