R之字符串相关

1.strsplit(m,n)? 分割字符串:将字符串m,在含有字符n的地方进行分割

?? 如：strsplit("abcdef","e"):??

结果为：

[[1]]
[1] "abcd" "f"?

?

strsplit(c("ab","cde","mnd"),"e")? 结果为：

[[1]]
[1] "ab"

[[2]]
[1] "cd"

[[3]]
[1] "mnd"

?

2.substr(m,index1,length):截取字符串m,从index1索引处截取长度为length的字符串；

> substr("abcde",1,3)
[1] "abc"

?

#字符串连接：
paste() #paste(...,sep = " ",collapse = NULL)

#字符串分割：
strsplit() #strsplit(x,split,extended = TRUE,fixed = FALSE,perl = FALSE)

#计算字符串的字符数：
nchar()

#字符串截取：
substr(x,start, stop)
substring(text,first,last = 1000000)
substr(x, stop) <- value
substring(text,last = 1000000) <- value

#字符串替换及大小写转换：
chartr(old,new, x)
tolower(x)
toupper(x)
casefold(x,upper = FALSE)

?

字符完全匹配
grep()
字符不完全匹配
agrep()
字符替换
gsub()
#以上这些函数均可以通过perl=TRUE来使用正则表达式。
???? grep(pattern,x,ignore.case = FALSE,extended = TRUE,
????????? perl = FALSE,value = FALSE,fixed = FALSE,useBytes = FALSE)

???? sub(pattern,replacement,
???????? ignore.case = FALSE,perl = FALSE,
???????? fixed = FALSE,useBytes = FALSE)

???? gsub(pattern,
????????? ignore.case = FALSE,
????????? fixed = FALSE,useBytes = FALSE)

???? regexpr(pattern,text, ignore.case = FALSE,
???????????? perl = FALSE,useBytes = FALSE)

???? gregexpr(pattern,
????????????? perl = FALSE,useBytes = FALSE)
See Also:

???? regular expression (aka 'regexp') for the details of the pattern
???? specification.

???? 'glob2rx' to turn wildcard matches into regular expressions.

???? 'agrep' for approximate matching.

???? 'tolower', 'toupper' and 'chartr' for character translations.
???? 'charmatch','pmatch', 'match'. 'apropos' uses regexps and has
???? nice examples.