根据R

Question

我对R相当陌生。我过去写过代码，当我不添加用户输入时我的脚本也起作用。我必须从2个txt文件路径中选择14个文件。每个都专门配对。 DS01与VDS1_1配对。我在环境寡妇中看到文件路径，它成功列出了文件。运行它时，没有任何错误。但是当我在交互模式下输入DS01时，我得到DS01对象不存在错误。

{ 
  askUser <- readline(prompt="Please, enter the data set (1-14) using DS# format:   ")
      SCpathname <-"E:/DS_textfiles/"
      list.files(path = SCpathname, pattern = "txt")
      VDSpathname <<-"E:/VDS/"
      list.files(path = VDSpathname, pattern = "txt")
       # to show the path works and files are there
  print(askUser) 


if (askUser== DS01){

   SCfilename =  "DS01.txt"
   VDSfilename = "VDS1_1.txt"
   SC120000 <- read.table(file=SCfilename, header=FALSE)
   VDS      <- read.table(file=VDSfilename, header=TRUE)

  }else if (askUser== DS02){
       SCfilename = " DS02.txt" 
       VDSfilename = "VDS2_1.txt"
       SC120000 <- read.table(file=SCfilename, header=FALSE)
       VDS      <- read.table(file=VDSfilename, header=TRUE)         

}else if (askUser== DS03){
     SCfilename = " DS03.txt" 
     VDSfilename = "VDS3_1.txt"
                SC120000 <- read.table(file=SCfilename, header=FALSE)
                VDS      <- read.table(file=VDSfilename, header=TRUE)     

   }else if (askUser==DS04 ){

       SCfilename = " DS04.txt" 
        VDSfilename = "VDS4_1.txt"
        SC120000 <- read.table(file=SCfilename, header=FALSE)
        VDS <- read.table(file=VDSfilename, header=TRUE)     

}else {
  return("Choose a different file number")
}
}