使用`read.csv`时如何防止定界符成为输入的一部分？

Question

我有如下的 csv 文件：

id,age,note
241,18,I am handsome,I am 18.
242,19, <ul>
    <li>
        <strong>I like music</strong><br />
        Talor swift：I kike Talor,I like her concert{smile}.<br />
        Beyonce:I have 3 albums.</li>
    <ul>
243,17,<I write something sn2370292kl@$^&,hahhaha

head是id,age,note，note是学生输入的字符串，可以是任意字符。

在 read.csv("qlist.csv",header=TRUE, sep=",",quote ="\"",na.strings = c(""," "),check.names=TRUE,fill=FALSE,strip.white = FALSE,comment.char = "",allowEscapes = FALSE,stringsAsFactors =FALSE,skipNul = FALSE) 中，我认为我不能使用 , 作为分隔符，因为 I am handsome,I am 18.

那么，可以使用哪种分隔符来防止分隔符成为输入的一部分呢？

另外，我尝试了 G. Grothendieck 的回答：

> version
               _                           
platform       x86_64-w64-mingw32          
arch           x86_64                      
os             mingw32                     
system         x86_64, mingw32             
status                                     
major          3                           
minor          5.3                         
year           2019                        
month          03                          
day            11                          
svn rev        76217                       
language       R                           
version.string R version 3.5.3 (2019-03-11)
nickname       Great Truth                 
> Lines <- 'id,age,note
+ 241,18,I am handsome,I am "18".
+ 242,19, <ul>
+ <li>
+ <strong>I like music</strong><br />
+ Talor swift：I kike Talor,I like her concert{smile}.<br />
+ Beyonce:I have 3 albums.</li>
+ <ul>
+ 243,17,<I write something sn2370292kl@$^&,hahhaha'
> L <- readLines(textConnection(Lines))
> L2 <- lapply(split(L, cumsum(grepl("^\S", L))), function(x) {
+     x <- gsub('"', '""', x)
+     x[1] <- sub('^(.*?,.*?,)', '\1"', x[1])
+     x[length(x)] <- paste0(x[length(x)], '"')
+     x
+ })
> DF <- read.csv(text = unname(unlist(L2)))
Warning message:
In scan(file = file, what = what, sep = sep, quote = quote, dec = dec,  :
  EOF within quoted string
> dim(DF)
[1] 5 3

Answer 1

我们需要在多行字段周围加上引号。首先使用 readLines 读入文件，将其拆分为逻辑记录并在第三个字段周围加上双引号。然后用 read.csv 阅读。

我们假设与变量 pat 中定义的 grep 模式匹配的行是不从前面的行继续的行。特别是，我们假设以数字、逗号、数字和逗号开头的行不会从前一行继续。如果该假设不成立，请适当修改 pat。

# L <- readLines("myfile.csv")
L <- readLines(textConnection(Lines))
# pat <- "^\S"  # this pattern worked for original input shown in question
pat <- "^\d+,\d+,"
L2 <- lapply(split(L, cumsum(grepl(pat, L))), function(x) {
  x <- gsub('"', '""', x)
  x[1] <- sub('^(.*?,.*?,)', '\1"', x[1])
  x[length(x)] <- paste0(x[length(x)], '"')
  x
})
DF <- read.csv(text = unname(unlist(L2)))
dim(DF)
## [1] 3 3

备注

Lines <- 'id,age,note
241,18,I am handsome,I am "18".
242,19, <ul>
    <li>
        <strong>I like music</strong><br />
        Talor swift：I kike Talor,I like her concert{smile}.<br />
        Beyonce:I have 3 albums.</li>
    <ul>
243,17,<I write something sn2370292kl@$^&,hahhaha'

使用`read.csv`时如何防止定界符成为输入的一部分？

How to prevent delimeter being the part of input when use `read.csv`?

r

ascii

delimiter

read.csv

备注