blocks|key|298906|text|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%2B1)
})|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|298907|这给了我们|unstyled|298908|[1]+"aa"+"bb"+"cc"+"cc"+"dd"|298909|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$B|C]]|$1|D|3|E|5|F|7|L|8|@]|9|@]|A|$]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$B|C]]|$1|I|3|-4|5|F|7|N|8|@]|9|@]|A|$]]]|J|$]]

<pre><code>string &lt;- "aabbccccdd"
# total length of string
num.chars &lt;- nchar(string)

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

# chop it up
sapply(starts, function(ii) {
 substr(string, ii, ii+1)
})
</code></pre>

Which gives

<pre><code>[1] "aa" "bb" "cc" "cc" "dd"
</code></pre>

blocks|key|515607|text|可以使用矩阵对字符进行分组：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|515608|s2+<-+function(x)+{
++m+<-+matrix(strsplit(x,+'')[[1]],+nrow=2)
++apply(m,+2,+paste,+collapse='')
}

s2('aabbccddeeff')
##+[1]+"aa"+"bb"+"cc"+"dd"+"ee"+"ff"|code-block|syntax|javascript|515609|不幸的是，对于奇数字符串长度的输入，这会中断，并给出一个警告：|515610|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]|515611|更不幸的是，对于奇数字符串长度的输入，@GSee中的g1和g2会默默返回错误的结果：|offset|length|style|CODE|515612|g1('abc')
##+[1]+"ab"

g2('abc')
##+[1]+"ab"+"cb"|515613|以下是遵循s2精神的函数，它接受每个组中的字符数的参数，并在必要时保留最后一项：|515614|s+<-+function(x,+n)+{
++sst+<-+strsplit(x,+'')[[1]]
++m+<-+matrix('',+nrow=n,+ncol=(length(sst)%2Bn-1)%25/%25n)
++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"+|515615|(它确实比g2慢，但比g1快大约7倍)|515616|entityMap^0|0|0|0|0|Q|2|T|2|0|0|0|0|5|2|B|2|0^^$0|@$1|2|3|4|5|6|7|10|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|11|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|12|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|13|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|14|8|@$M|15|N|16|O|P]|$M|17|N|18|O|P]]|9|@]|A|$]]|$1|Q|3|R|5|D|7|19|8|@]|9|@]|A|$E|F]]|$1|S|3|T|5|6|7|1A|8|@]|9|@]|A|$]]|$1|U|3|V|5|D|7|1B|8|@]|9|@]|A|$E|F]]|$1|W|3|X|5|6|7|1C|8|@$M|1D|N|1E|O|P]|$M|1F|N|1G|O|P]]|9|@]|A|$]]|$1|Y|3|-4|5|6|7|1H|8|@]|9|@]|A|$]]]|Z|$]]

One can use a matrix to group the characters:

<pre><code>s2 &lt;- function(x) {
 m &lt;- matrix(strsplit(x, '')[[1]], nrow=2)
 apply(m, 2, paste, collapse='')
}

s2('aabbccddeeff')
## [1] "aa" "bb" "cc" "dd" "ee" "ff"
</code></pre>

Unfortunately, this breaks for an input of odd string length, giving a warning:

<pre><code>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]
</code></pre>

More unfortunate is that <code>g1</code> and <code>g2</code> from @GSee silently return incorrect results for an input of odd string length:

<pre><code>g1('abc')
## [1] "ab"

g2('abc')
## [1] "ab" "cb"
</code></pre>

Here is function in the spirit of s2, taking a parameter for the number of characters in each group, and leaves the last entry short if necessary:

<pre><code>s &lt;- function(x, n) {
 sst &lt;- strsplit(x, '')[[1]]
 m &lt;- matrix('', nrow=n, ncol=(length(sst)+n-1)%/%n)
 m[seq_along(sst)] &lt;- 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" 
</code></pre>

(It is indeed slower than <code>g2</code>, but faster than <code>g1</code> by about a factor of 7)

blocks|key|299017|text|虽然丑陋，但很管用|type|unstyled|depth|inlineStyleRanges|entityRanges|data|299018|sequenceString+<-+"ATGAATAAAG"

J=3#maximum+sequence+length+in+file
sequenceSmallVecStart+<-
++substring(sequenceString,+seq(1,+nchar(sequenceString)-J%2B1,+J),+
++++seq(J,nchar(sequenceString),+J))
sequenceSmallVecEnd+<-
++++substring(sequenceString,+max(seq(J,+nchar(sequenceString),+J))%2B1)
sequenceSmallVec+<-
++++c(sequenceSmallVecStart,sequenceSmallVecEnd)
cat(sequenceSmallVec,sep+=+"\n")|code-block|syntax|javascript|299019|提供ATG+AAT+AAA+G|299020|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

Ugly but works 

<pre><code>sequenceString &lt;- "ATGAATAAAG"

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

Gives 
 ATG
 AAT
 AAA
 G

I have a string such as:

<code>"aabbccccdd"</code>

I want to break this string into a vector of substrings of length 2 :

<code>"aa" "bb" "cc" "cc" "dd"</code>

How to split a string into substrings of a given length?

我有一个字符串，例如："aabbccccdd"我想把这个字符串分解成一个长度为2的子字符串的向量："aa" "bb" "cc" "cc" "dd"

问如何将字符串拆分成给定长度的子串？
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