一、函数功能介绍
- LETTER[]：生成26个大写英文字母；
- letters[]：生成26个小写英文字母；
- month.abb[]:英文月份缩写
- month.name[]：一年中的12个英文名字
- pi[]:圆周率
二、代码演示
1.LETTER[]：生成26个大写英文字母；
<=26个：
LETTERS[1:26]
[1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O"
[16] "P" "Q" "R" "S" "T" "U" "V" "W" "X" "Y" "Z"
大于27个,之后的为"NA"
LETTERS[1:27]
[1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O"
[16] "P" "Q" "R" "S" "T" "U" "V" "W" "X" "Y" "Z" NA
> LETTERS[1:30]
[1] "A" "B" "C" "D" "E" "F" "G" "H" "I" "J" "K" "L" "M" "N" "O"
[16] "P" "Q" "R" "S" "T" "U" "V" "W" "X" "Y" "Z" NA NA NA NA
检索第几个：
LETTERS[10]
[1] "J"
> LETTERS[20]
[1] "T"
letters[]：生成26个小写英文字母；
letters[1:26]
[1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o"
[16] "p" "q" "r" "s" "t" "u" "v" "w" "x" "y" "z"
letters[1:30]
[1] "a" "b" "c" "d" "e" "f" "g" "h" "i" "j" "k" "l" "m" "n" "o"
[16] "p" "q" "r" "s" "t" "u" "v" "w" "x" "y" "z" NA NA NA NA
英文月份：
> month.abb[1:12]
[1] "Jan" "Feb" "Mar" "Apr" "May" "Jun" "Jul" "Aug" "Sep" "Oct"
[11] "Nov" "Dec"
month.name[1:12]
[1] "January" "February" "March" "April" "May"
[6] "June" "July" "August" "September" "October"
[11] "November" "December"
pi[]:圆周率
pi[]
[1] 3.141593
总结：
