On Aug 6, 2012, at 12:06 PM, Marc Schwartz <marc_schwa...@me.com> wrote:
> Perhaps I am missing something, but why use sapply() when grepl() is already
> vectorized?
>
> is.letter <- function(x) grepl("[:alpha:]", x)
> is.number <- function(x) grepl("[:digit:]", x)
Sorry, typos in the above from my C&P. Should be:
is.letter <- function(x) grepl("[[:alpha:]]", x)
is.number <- function(x) grepl("[[:digit:]]", x)
Marc
>
> x <- c(letters, 1:26)
>
> x[1:10] <- paste(x[1:10], sample(1:10, 10), sep='')
>
> x <- rep(x, 1e3)
>
>> str(x)
> chr [1:52000] "a2" "b10" "c8" "d3" "e6" "f1" "g5" ...
>
>> system.time(is.letter(x))
> user system elapsed
> 0.011 0.000 0.010
>
>> system.time(is.number(x))
> user system elapsed
> 0.010 0.000 0.011
>
>
> Regards,
>
> Marc Schwartz
>
> On Aug 6, 2012, at 11:51 AM, Rui Barradas <ruipbarra...@sapo.pt> wrote:
>
>> Hello,
>>
>> Fun as an exercise in vectorization. 30 times faster. Don't look, guess.
>>
>> Gave it up? Ok, here it is.
>>
>>
>> is_letter <- function(x, pattern=c(letters, LETTERS)){
>> sapply(x, function(y){
>> any(sapply(pattern, function(z) grepl(z, y, fixed=T)))
>> })
>> }
>> # test ascii codes, just one loop.
>> has_letter <- function(x){
>> sapply(x, function(y){
>> y <- as.integer(charToRaw(y))
>> any((65 <= y & y <= 90) | (97 <= y & y <= 122))
>> })
>> }
>>
>> x <- c(letters, 1:26)
>> x[1:10] <- paste(x[1:10], sample(1:10, 10), sep='')
>> x <- rep(x, 1e3)
>>
>> t1 <- system.time(is_letter(x))
>> t2 <- system.time(has_letter(x))
>> rbind(t1, t2, t1/t2)
>> user.self sys.self elapsed user.child sys.child
>> t1 15.69 0 15.74 NA NA
>> t2 0.50 0 0.50 NA NA
>> 31.38 NaN 31.48 NA NA
>>
>>
>> Em 06-08-2012 17:25, Liviu Andronic escreveu:
>>> Dear all
>>> I'm pretty sure that I'm approaching the problem in a wrong way.
>>> Suppose the following character vector:
>>>> (x[1:10] <- paste(x[1:10], sample(1:10, 10), sep=''))
>>> [1] "a10" "b7" "c2" "d3" "e6" "f1" "g5" "h8" "i9" "j4"
>>>> x
>>> [1] "a10" "b7" "c2" "d3" "e6" "f1" "g5" "h8" "i9" "j4" "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"
>>>
>>>
>>> How do you test whether the elements of the vector contain at least
>>> one letter (or at least one digit) and obtain a logical vector of the
>>> same dimension? I came up with the following awkward function:
>>> is_letter <- function(x, pattern=c(letters, LETTERS)){
>>> sapply(x, function(y){
>>> any(sapply(pattern, function(z) grepl(z, y, fixed=T)))
>>> })
>>> }
>>>
>>>> is_letter(x)
>>> a10 b7 c2 d3 e6 f1 g5 h8 i9 j4 k
>>> l m n o
>>> TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
>>> TRUE TRUE TRUE TRUE
>>> p q r s t u v w x y z
>>> 1 2 3 4
>>> TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
>>> FALSE FALSE FALSE FALSE
>>> 5 6 7 8 9 10 11 12 13 14 15
>>> 16 17 18 19
>>> FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
>>> FALSE FALSE FALSE FALSE
>>> 20 21 22 23 24 25 26
>>> FALSE FALSE FALSE FALSE FALSE FALSE FALSE
>>>> is_letter(x, 0:9) ##function slightly misnamed
>>> a10 b7 c2 d3 e6 f1 g5 h8 i9 j4 k
>>> l m n o
>>> TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE FALSE
>>> FALSE FALSE FALSE FALSE
>>> p q r s t u v w x y z
>>> 1 2 3 4
>>> FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE FALSE
>>> TRUE TRUE TRUE TRUE
>>> 5 6 7 8 9 10 11 12 13 14 15
>>> 16 17 18 19
>>> TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE TRUE
>>> TRUE TRUE TRUE TRUE
>>> 20 21 22 23 24 25 26
>>> TRUE TRUE TRUE TRUE TRUE TRUE TRUE
>>>
>>>
>>> Is there a nicer way to do this? Regards
>>> Liviu
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
