R strsplit 保留最后一个空元素为空字符串

Question

R的strsplit如果为“空”(示例 2)，则删除最后一个元素，但不会在第一个元素(示例 3)或在要拆分的向量中间(示例 4)时删除。

> unlist(strsplit(x = "1,4", split = ",")) #Example 1
[1] "1" "4"
> unlist(strsplit(x = ",4", split = ",")) #Example 2
[1] ""  "4"
> unlist(strsplit(x = "1,", split = ",")) #Example 3
[1] "1"
> unlist(strsplit(x = "1,,,4", split = ",")) #Example 4
[1] "1" ""  ""  "4"

有没有办法解析字符串，如果 split 后为空，则允许保留最后一个元素:

> strmagic(x = "1,", split = ",") #strmagic being the wanted function
[1] "1" ""

其他软件包的解决方案是 here (似乎)。可以在基础 R 中完成吗？

更新

是否需要添加填充元素，然后是 la:

strmagic <- function(v, sep)lapply(v, function(x)head(unlist(strsplit(paste(x, "-", sep = sep), split = sep)), -1))

Answer 1

奇怪的。这有效，但不是最有效的。 ZAQ 只是一组随机字符

sp <- function( X ){
    X <- paste0( X, "ZAQ" )
    X <- unlist(strsplit(x = X, split = ","))
    X <- gsub( "ZAQ" ,"" ,X) 
    X
}
sp("1,4")
sp(",4")
sp("1,")
sp("1,,,4")