【R语言】常用的字符串处理函数【待更新】-优快云博客

本文介绍了R语言中字符串的各种操作方法，包括连接、分割、截取、替换等，并详细讲解了如何利用grep、agrep等函数进行字符串匹配和搜索，适用于需要处理文本数据的读者。

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#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)

例如.

strsplit('123abcdefgabcdef','ab')
[[1]]
[1] "123" "cdefg" "cdef"

#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, start, stop) <- value
substring(text, first, 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)

#匹配相关的函数：

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, x,
         ignore.case = FALSE, extended = TRUE, perl = FALSE,
         fixed = FALSE, useBytes = FALSE)

     gsub(pattern, replacement, x,
          ignore.case = FALSE, extended = TRUE, perl = FALSE,
          fixed = FALSE, useBytes = FALSE)

     regexpr(pattern, text, ignore.case = FALSE, extended = TRUE,
             perl = FALSE, fixed = FALSE, useBytes = FALSE)

     gregexpr(pattern, text, ignore.case = FALSE, extended = TRUE,
              perl = FALSE, fixed = 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.