strsplit返回一个列表，因此可以使用unlist将字符串强制转换为单个字符向量，或者使用列表索引[[1]]访问第一个元素。

x <- paste(LETTERS, collapse = "")

unlist(strsplit(x, split = ""))
# [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S"
#[20] "T" "U" "V" "W" "X" "Y" "Z"

OR（请注意，实际上不需要命名split参数）

strsplit(x, "")[[1]]
# [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S"
#[20] "T" "U" "V" "W" "X" "Y" "Z"

您也可以在NULL或character(0)上分割，以取得相同的结果。

stringr中的str_extract_all()提供了一种很好的方法来执行此操作：

str_extract_all("ABCDEFGHIJKLMNOPQRSTUVWXYZ", boundary("character"))

[[1]]
 [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S" "T" "U"
[22] "V" "W" "X" "Y" "Z"

由于stringr 1.5.0，您可以使用str_split_1，str_split的一个版本，用于单个字符串：

library(stringr)
x <- paste(LETTERS, collapse = "")
str_split_1(x, "")
# [1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O" "P" "Q" "R" "S"
#[20] "T" "U" "V" "W" "X" "Y" "Z"

This is rendered stepwise for clarity; in practice, a function would be created.
To find the number of times any character is repeated in sequence

the_string <- "BaaaaaaH"
# split string into characters
the_runs <- strsplit(the_string, "")[[1]]
# find runs
result <- rle(the_runs)
# find values that are repeated
result$values[which(result$lengths > 1)]
#> [1] "a"
# retest with more runs
the_string <- "BaabbccH"
# split string into characters
the_runs <- strsplit(the_string, "")[[1]]
# find runs
result <- rle(the_runs)
# find values that are repeated
result$values[which(result$lengths > 1)]
#> [1] "a" "b" "c"