问如何将字符串拆分成给定长度的子串？

EN

string <- "aabbccccdd"
# total length of string
num.chars <- nchar(string)

# the indices where each substr will start
starts <- seq(1,num.chars, by=2)

# chop it up
sapply(starts, function(ii) {
  substr(string, ii, ii+1)
})

[1] "aa" "bb" "cc" "cc" "dd"

s2 <- function(x) {
  m <- matrix(strsplit(x, '')[[1]], nrow=2)
  apply(m, 2, paste, collapse='')
}

s2('aabbccddeeff')
## [1] "aa" "bb" "cc" "dd" "ee" "ff"

s2('abc')
## [1] "ab" "ca"
## Warning message:
## In matrix(strsplit(x, "")[[1]], nrow = 2) :
##   data length [3] is not a sub-multiple or multiple of the number of rows [2]

g1('abc')
## [1] "ab"

g2('abc')
## [1] "ab" "cb"

s <- function(x, n) {
  sst <- strsplit(x, '')[[1]]
  m <- matrix('', nrow=n, ncol=(length(sst)+n-1)%/%n)
  m[seq_along(sst)] <- sst
  apply(m, 2, paste, collapse='')
}

s('hello world', 2)
## [1] "he" "ll" "o " "wo" "rl" "d" 
s('hello world', 3)
## [1] "hel" "lo " "wor" "ld" 

sequenceString <- "ATGAATAAAG"

J=3#maximum sequence length in file
sequenceSmallVecStart <-
  substring(sequenceString, seq(1, nchar(sequenceString)-J+1, J), 
    seq(J,nchar(sequenceString), J))
sequenceSmallVecEnd <-
    substring(sequenceString, max(seq(J, nchar(sequenceString), J))+1)
sequenceSmallVec <-
    c(sequenceSmallVecStart,sequenceSmallVecEnd)
cat(sequenceSmallVec,sep = "\n")