“数据”必须是二维的（例如数据框或矩阵）RShiny

Question

我正在使用Shiny App，遇到一条错误消息，提示数据需要为二维。

该应用程序的目的是基于称为区域的列过滤数据集，并查看和更新​​数据集。应该很简单...不过，用户需要先上传数据集才能使用该应用程序。我假设此应用程序中使用的所有文件都会有一个列，即“区域”。我相信问题出在“＃选择要打印的区域----”。

UI：

 library(shiny)
 library(DT)
 library(tidyverse)

 # Define UI for data upload app ----
 ui <- fluidPage(

   # App title ----
   titlePanel(title = h1("Upload file and select columns", align = "center")),

   # Sidebar layout with input and output definitions ----
   sidebarLayout(

     # Sidebar panel for inputs ----
     sidebarPanel(

       # Input: Select a file ----
       fileInput("uploaded_file", "Choose CSV File",
                 multiple = TRUE,
                 accept = c("text/csv",
                            "text/comma-separated-values,text/plain",
                            ".csv")),

       # Horizontal line ----
       tags$hr(),

       # Input: Checkbox if file has header ----
       checkboxInput("header", "Header", TRUE),

       # Input: Select separator ----
       radioButtons("sep", "Separator",
                    choices = c(Semicolon = ";",
                                Comma = ",",
                                Tab = "\t"),
                    selected = ","),


       # Horizontal line ----
       tags$hr(),

       # Input: Select number of rows to display ----
       radioButtons("disp", "Display",
                    choices = c(All = "all",
                                Head = "head"),
                    selected = "all"),

       # Select variables to display ----
  # uiOutput("variables"),

       # Select variables to display ----
       uiOutput("regions")

     ),

     # Main panel for displaying outputs ----
     mainPanel(

       tabsetPanel(
         id = "dataset",
         tabPanel("Data Explorer", div(style = "overflow-x: scroll",dataTableOutput("rendered_file")))
       )
     )

   )
 )

服务器：

# Define server logic to read selected file ----
server <- function(input, output, session) {

  # Read file ----
  df <- reactive({
    req(input$uploaded_file)
    read.csv(input$uploaded_file$datapath,
             header = input$header,
             sep = input$sep)  

  })

  output$regions <- renderUI({
    selectizeInput(inputId = "select_region", 
                   label = "Select region of interest", 
                   choices = unique(df()$region),
                   multiple = T, 
                   options = list(placeholder = 'Select the region of interest'))
  })

  # Select regions to print ----
  df_sel <- reactive({
    req(input$select_region)
    df_sel <- df()$region == input$select_region

  })


  # Print data table ----  
  output$rendered_file <- DT::renderDataTable({
    if(input$disp == "head") {
      head(df_sel())
    }
    else {
      df_sel()
    }
  })

}