R中三个级别的下拉列表

Question

I want do make a menu to selection schools. But the schools are nested in citys and this on departments so I need to this in a drop down list of three leves. This code works well for departments and citys. But when I expand for schools it gives me a error

Thanks

require(shiny)

datas <- data.frame(directory = c(puntaje_2016_1$estu_reside_depto), file = c(puntaje_2016_1$estu_reside_mcpio) , cole = c(puntaje_2016_1$cole_nombre_sede) )


runApp(list(
  ui = basicPage(
    sidebarPanel(
      selectInput("directory", "Select a directory", choices = levels(datas$directory), selected = levels(datas$directory)[1]),
      tags$hr(),
      selectInput("files", "Select files", choices = datas$file[datas$directory == levels(datas$directory)[1]], multiple = FALSE)
     ## tags$hr()
      ##selectInput("cole", "Select files", choices = datas$cole[datas$file == levels(datas$file)[1]], multiple = FALSE)
          )
  ),
  server = function(input, output, session) {

observe({
  directory <- input$directory
  updateSelectInput(session, "files", choices = datas$file[datas$directory == directory])
      })
##observe({
  ##files<-input$files 
  ##updateSelectInput(session, "coles", choice = datas$cole[datas$file == ##files])
   ## })
  }
))

Answer 1

You don't have to do this:

datas$file[datas$directory == directory]

You can just do this:

unique(data$file$directory)