r - 为什么 fread 将回车 (\r) 插入 data.table？

Question

我正在使用 data.table::fread 从 .csv 文件中读取数据在 Windows 10 计算机上。数据通过read.csv正确读入;但是，当我使用 fread 时要读入数据，结果数据表的每一行中的所有最后列都以 \r 结尾，大概表示回车。这会导致数字字段被赋予字符数据类型。 (而不是数字文字 4.53 ，行尾单元格将包含字 rune 字 4.53\r 。)

为什么会出现这个bug？有没有办法通过fread的函数调用直接解决这个问题？ ?

更新

当 verbose = TRUE 时，我得到以下信息使用参数

Input contains no \n. Taking this to be a filename to open
File opened, filesize is 0.000001 GB.
Memory mapping ... ok
Detected eol as \n only (no \r afterwards), the UNIX and Mac standard.
Positioned on line 1 after skip or autostart
This line is the autostart and not blank so searching up for the last non-blank ... line 1
Detecting sep ... ','
Detected 7 columns. Longest stretch was from line 1 to line 13
Starting data input on line 1 (either column names or first row of data). First 10 characters: subjectNum
All the fields on line 1 are character fields. Treating as the column names.
Count of eol: 13 (including 1 at the end)
Count of sep: 72
nrow = MIN( nsep [72] / ncol [7] -1, neol [13] - nblank [1] ) = 12
Type codes (   first 5 rows): 1131414
Type codes: 1131414 (after applying colClasses and integer64)
Type codes: 1131414 (after applying drop or select (if supplied)
Allocating 7 column slots (7 - 0 dropped)
Read 12 rows. Exactly what was estimated and allocated up front
   0.000s (  0%) Memory map (rerun may be quicker)
   0.001s ( 33%) sep and header detection
   0.000s (  0%) Count rows (wc -l)
   0.002s ( 67%) Column type detection (first, middle and last 5 rows)
   0.000s (  0%) Allocation of 12x7 result (xMB) in RAM
   0.000s (  0%) Reading data
   0.000s (  0%) Allocation for type bumps (if any), including gc time if triggered
   0.000s (  0%) Coercing data already read in type bumps (if any)
   0.000s (  0%) Changing na.strings to NA
   0.003s        Total

Answer 1

如果您的文件看起来像 x="a\n1\r\n2\r\n" ，然后 fread(x)将给出描述的结果:

     a
1: 1\r
2: 2\r

出现这种情况是因为行尾指示符跨行不一致。

我听说其他人发生了这种情况，但我不确定它来自哪里，或者是否有比“修复”文件更好的方法来解决它，可能是使用命令行工具。