r - 如何在R中分割字符同时保留括号内的内容？

Question

我有一些氨基酸修饰，例如:

example <- c('_(Acetyl (Protein N-term))DDDIAAM(Oxidation (M))CK_')

我想将这样的序列拆分成类似于以下的状态:

example2 <- c('_','(Acetyl (Protein N-term))','D','D','D','I','A','A','M','(Oxidation (M))','C','K','_')

但是我不知道如何拆分这样的字符串，同时将内容保留在括号内，是否有任何函数或代码可以帮助我做到这一点？

谢谢， 李李

Answer 1

更新

借鉴@benson23的想法通过插入特殊字符，例如 @ ，我们可以使用 strsplit 尝试下面的代码+ 嵌套 (g)sub的

unlist(
  lapply(
    unlist(
      strsplit(
        sub(
          "(.*)\\)", "\\1)@",
          sub(
            "\\(", "@(",
            gsub("(\\))([^()]+)(\\()", "\\1@\\2@\\3", example)
          )
        ), "@"
      )
    ),
    function(s) {
      if (startsWith(s, "(")) {
        s
      } else {
        strsplit(s, "")
      }
    }
  )
)

---

这是一个庞大的实现，用于查找配对的括号并进行拆分

# split string by characters
v <- unlist(strsplit(example, ""))

# positions of "(" and ")"
a <- which(v == "(")
b <- which(v == ")")

# split as per the position of ")"
lst1 <- split(v, cumsum(replace(rep(0, length(v)), 1 + by(b, findInterval(b, a), max), 1)))

# split as per the position of "("
lst2 <- unlist(lapply(lst1, function(x) split(x, cumsum(x == "(") > 0)), recursive = FALSE)

# output
res <- unlist(
  lapply(
    lst2,
    function(s) {
      if (s[1] == "(") {
        paste0(s, collapse = "")
      } else {
        s
      }
    }
  ),
  use.names = FALSE
)

测试

让我们尝试一个有点棘手的例子 example <- c("_(Acetyl (Protein (N-term)) XXX) DDDIAAM(Oxidation (M))CK_") ，我们会看到res作为

 [1] "_"                               "(Acetyl (Protein (N-term)) XXX)"
 [3] " "                               "D"
 [5] "D"                               "D"
 [7] "I"                               "A"
 [9] "A"                               "M"
[11] "(Oxidation (M))"                 "C"
[13] "K"