On Mon, Aug 6, 2012 at 7:35 PM, Marc Schwartz <marc_schwa...@me.com> wrote:
> is.letter <- function(x) grepl("[[:alpha:]]", x)
> is.number <- function(x) grepl("[[:digit:]]", x)
>
Another follow-up. To test for (non-)alphanumeric one would do the following:
> x <- c(letters, 1:26, '+', '-', '%^&')
> x[1:10] <- paste(x[1:10], 1:10, sep='')
> x
[1] "a1" "b2" "c3" "d4" "e5" "f6" "g7" "h8" "i9" "j10" "k"
"l" "m" "n"
[15] "o" "p" "q" "r" "s" "t" "u" "v" "w" "x" "y"
"z" "1" "2"
[29] "3" "4" "5" "6" "7" "8" "9" "10" "11" "12" "13"
"14" "15" "16"
[43] "17" "18" "19" "20" "21" "22" "23" "24" "25" "26" "+"
"-" "%^&"
> xb <- grepl("[[:alnum:]]",x) ##test for alphanumeric chars
> x[xb]
[1] "a1" "b2" "c3" "d4" "e5" "f6" "g7" "h8" "i9" "j10" "k"
"l" "m" "n"
[15] "o" "p" "q" "r" "s" "t" "u" "v" "w" "x" "y"
"z" "1" "2"
[29] "3" "4" "5" "6" "7" "8" "9" "10" "11" "12" "13"
"14" "15" "16"
[43] "17" "18" "19" "20" "21" "22" "23" "24" "25" "26"
> xb <- grepl("[[:punct:]]",x) ##test for non-alphanumeric chars
> x[xb]
[1] "+" "-" "%^&"
More regex rules are available on the Wiki [1]. Regards
Liviu
[1] http://en.wikipedia.org/wiki/Regular_expression
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