如何在R语言中读取文本文件并过滤非英文字符行

有一个.txt文件内容如下：

*** Header Start ***
਍嘀攀爀猀椀漀渀倀攀爀猀椀猀琀㨀 ㄀ഀഀ
LevelName: Session
਍䰀攀瘀攀氀一愀洀攀㨀 䈀氀漀挀欀ഀഀ
LevelName: Trial
਍䰀攀瘀攀氀一愀洀攀㨀 匀甀戀吀爀椀愀氀ഀഀ
LevelName: LogLevel5
਍䰀攀瘀攀氀一愀洀攀㨀 䰀漀最䰀攀瘀攀氀㘀ഀഀ
LevelName: LogLevel7
਍䰀攀瘀攀氀一愀洀攀㨀 䰀漀最䰀攀瘀攀氀㠀ഀഀ

需要读取文件并移除所有含乱码的行，仅保留英文行作为数据框的一列。但使用read.table、readLines、scan或read_delim读取时，因乱码出现如下异常输出：

[1] "ÿþ*" "H"   "S"   "*"   "\n"  "V"   "1"   "\n"  "L"   "S"   "\n"  "L"   "B"   "\n"  "L"   "T"   "\n" 
  [18] "L"   "S"   "\n"  "L"   "L"   "\n"  "L"   "L"   "\n"  "L"   "L"   "\n"  "L"   "L"   "\n"  "L"   "L"  
  [35] "\n"  "L"   "L"   "\n"  "E"   "G"   "\n"  "S"   "0"   "\n"  "S"   "1"   "\n"  "S"   "8"   "4"   "P"  
  [52] "\n"  "S"   "9"   "\n"  "S"   "1"   "\n"  "D"   "G"   "\n"  "R"   "-"   "\n"  "G"   "1"   "\n"  "D"  

如何无需手动删除乱码行解决该问题？

1. 指定正确编码读取文件
   输出开头的ÿþ是UTF-16LE编码的BOM（字节顺序标记），读取时指定对应编码可避免字符被拆分：

   lines <- readLines("your_file.txt", encoding = "UTF-16LE")
   

2. 过滤乱码行
   使用正则表达式筛选仅包含ASCII字符的行，排除含非ASCII乱码的内容，同时移除空行：

   clean_lines <- lines[grepl("^[[:ascii:]]+$", lines) & lines != ""]
   

3. 转换为数据框
   将清理后的行转为数据框的一列：

   # Base R 实现
   df <- data.frame(Level_Info = clean_lines, stringsAsFactors = FALSE)
   
   # Tidyverse 实现（需先加载tibble包）
   library(tibble)
   df <- tibble(Level_Info = clean_lines)
   

最终结果 #

处理后的数据框仅保留以下有效行：

*** Header Start ***
LevelName: Session
LevelName: Trial
LevelName: LogLevel5
LevelName: LogLevel7

内容的提问来源于stack exchange，提问作者jc2525