R語言處理字串

用於字串分割的函式：

如strsplit(

'123abcdefgabcdef',

'ab')

[[1]]

[1]

"123"

"cdefg"

"cdef"

#字串連線：

paste()

#paste(..., sep = "", collapse = null)

#字串分割：

strsplit()

#strsplit(x, split, extended = true, fixed =false, perl = false)

#計算字串的字元數：

nchar()

#字串擷取：

substr(x,

start,

stop)

substring(

text, first, last =

1000000)

substr(x,

start,

stop)<- value

substring(

text, first, last =

1000000) <- value

###########例子說明

substr("abcdef",2,4)

substring("abcdef",1:6,1:6)## strsplit is more efficient ...

substr(rep("abcdef",4),1:4,4:5)

x <- c("asfef", "qwerty", "yuiop[", "b","stuff.blah.yech")

substr(x, 2, 5)substring(x, 2, 4:6)

substring(x, 2) <- c("..", "+++") x

###########

#字串替換及大小寫轉換：

chartr(old,

new,x)

tolower(x)

toupper(x)

casefold(x, upper =

false)

字元完全匹配

grep()

字元不完全匹配

agrep()

字元替換

gsub()

#以上這些函式均可以通過perl=true來使用正規表示式。

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')forthe details of the pattern

specification.

'glob2rx' to turn wildcard matches into regularexpressions.

'agrep'for

'chartr'forcharacter translations.

'charmatch',

'pmatch',

'match'.

'apropos' uses regexps and has

niceexamples.

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