R 数据转换
只提供函数与功能关键字速查，具体用法可自己搜索官方文档，示例比较详尽。
字符串
# 获取字符串长度
nchar()
# 字符串分割
strsplit()
# 字符串拼接
paste(, sep="")
# 字符串截取
substr()
# 字符串替代
gsub()
chartr()
sub()
# 字符串匹配
grep()
# 大小写替换
toupper()
tolower()
数字
# 取整
## 向下
floor(...)
## 向上
ceiling(...)
## 四舍五入
round(...)
# 有效数字
## 小数点后开始
round(...)
## 从头开始
signif(...)
# 科学计数法
format(, scientific = T)
# 补零补位
sprintf('%03d', 1)
# 千分位间隔
prettyNum(, big.mark = ',')时间
POSIXlt
> today<-Sys.time()
> unclass(as.POSIXlt(today))
$sec
[1] 53.27151
$min
[1] 38
$hour
[1] 20
$mday
[1] 6
$mon
[1] 5
$year
[1] 116
$wday
[1] 1
$yday
[1] 157
$isdst
[1] 0
$zone
[1] "CST"
$gmtoff
[1] 28800
attr(,"tzone")正则表达式
R 字符串处理支持在pattern使用正则表达式[1]
'\n' newline
'\r' carriage return
'\t' tab
'\b' backspace
'\a' alert (bell)
'\f' form feed
'\v' vertical tab
'\\' backslash '\'
'\'' ASCII apostrophe '''
'\"' ASCII quotation mark '"'
'\`' ASCII grave accent (backtick) '`'
'\nnn' character with given octal code (1, 2 or 3 digits)
'\xnn' character with given hex code (1 or 2 hex digits)
'\unnnn' Unicode character with given code (1-4 hex digits)
'\Unnnnnnnn' Unicode character with given code (1-8 hex digits)
[:alnum:]
Alphanumeric characters: [:alpha:] and [:digit:].
[:alpha:]
Alphabetic characters: [:lower:] and [:upper:].
[:blank:]
Blank characters: space and tab, and possibly other locale-dependent characters such as non-breaking space.
[:cntrl:]
Control characters. In ASCII, these characters have octal codes 000 through 037, and 177 (DEL). In another character set, these are the equivalent characters, if any.
[:digit:]
Digits: 0 1 2 3 4 5 6 7 8 9.
[:graph:]
Graphical characters: [:alnum:] and [:punct:].
[:lower:]
Lower-case letters in the current locale.
[:print:]
Printable characters: [:alnum:], [:punct:] and space.
[:punct:]
Punctuation characters:
! " # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \ ] ^ _ ` { | } ~.
[:space:]
Space characters: tab, newline, vertical tab, form feed, carriage return, space and possibly other locale-dependent characters.
[:upper:]
Upper-case letters in the current locale.
[:xdigit:]
Hexadecimal digits:
0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f.详见[2]
