用于字符串分割的函数:
如
strsplit('123abcdefgabcdef','ab')
[[1]]
[1]
#字符串连接:
paste()
sep = " ", collapse = NULL)
#字符串分割:
strsplit()
split, extended = TRUE, fixed = FALSE, perl = FALSE)
#计算字符串的字符数:
nchar()
#字符串截取:
substr(x,
substring(text,
first, last =
substr(x,
<- value
substring(text,
first, last =
<- value
###########例子说明
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
###########
#字符串替换及大小写转换:
chartr(old,
x)
tolower(x)
toupper(x)
casefold(x,
upper =
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。
x, ignore.case =
extended =
value =
useBytes =
extended =
extended =
=
See Also:
details of the pattern
regexps and has