r - R中strsplit（）的奇怪行为？

Question

我想使用strsplit()x = "a,b,"将字符串（最后一个位置的逗号）拆分为向量。c("a","b","")

结果是：

>strsplit(x,',')
[[1]]
[1] "a" "b"

我想要第三个组件（空字符串或 NULL）。

该功能read.csv(x)可以管理它，但我仍然认为它strsplit()应该像我预期的那样运行。Python 提供c("a","b","").

也许有一些strsplit()我不知道的选择？

Answer 1

这就是它的工作原理，并记录在帮助（strsplit）中：

 Note that this means that if there is a match at the beginning of
 a (non-empty) string, the first element of the output is ‘""’, but
 if there is a match at the end of the string, the output is the
 same as with the match removed.

您可能希望str_split从stringr包中使用：

> require(stringr)
> str_split("a,b,",",")
[[1]]
[1] "a" "b" "" 

> str_split("a,b",",")
[[1]]
[1] "a" "b"

> str_split(",a,b",",")
[[1]]
[1] ""  "a" "b"

> str_split(",a,b,,,",",")
[[1]]
[1] ""  "a" "b" ""  ""  ""