R/Shiny：使用来自上传文件的标题填充 SelectInput 选项

Question

I'm trying to build a page using R Shiny that has:

• A File Widget for uploading CSV files

• A SelectInput component

I'd like to use these as follows:

• Upon uploading a valid CSV file, populate the SelectInput whose options are the headers from the CSV file, the first header being the default selected

I've tried various forms of observe() and observeEvent() so far, but have had no success in getting this even close. Any suggestions you may have would be great.

Answer 1

Here's an option -

library(shiny)

#Sample data
#write.csv(mtcars, 'data.csv', row.names = FALSE)

ui <- fluidPage(
  fileInput('file', 'Upload csv file'),
  uiOutput('dropdown')
)

server <- function(input, output) {
  data <- reactive({
    req(input$file)
    read.csv(input$file$datapath)
  })
  
  output$dropdown <- renderUI({
    req(data())
    selectInput('cols', 'Select Column', names(data()))
  })
}


shinyApp(ui, server)