[R] regular expression help

[William Dunlap]

> what's the difference between [:space:]+ and[[:space:]]+ ?

The pattern '[:space:]' matches any of ':', 's', 'p', 'a', 'c', and
'e' (the second colon is superfluous).  I.e., it has no magic meaning.
Inside of [] it does have a special meaning.

The pattern '[[:space:]]' matches a space, a newline, and other
whitespace characters.  The pattern '[a-c[:space:]z[:digit:]]' matches
'a', 'b', 'c', any decimal digit, and any whitespace character.
Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Fri, Jun 27, 2014 at 6:27 AM, C Lin <baccts at hotmail.com> wrote:
> Thank you all for your help.
>
> Bill, thanks for making it compact and I did mean any amount of whitespace.
>
> To break it down, so I know why this pattern work:
> The first parenthesis means that before AARSD1 it can be
> ^: begins with nothing
> |: or
> //: double slash or
> [[:space:]]+: one or more whitespace character
>
> For the second parenthesis:
> $: ending with nothing
>
> Do this sound correct?
>
> I missed the fact that I need the ^ and $ and I always do [:space:]+ instead of [[:space:]]+
> what's the difference between [:space:]+ and[[:space:]]+ ?
>
> Thanks so much!
> Lin
>
> ----------------------------------------
>> From: wdunlap at tibco.com
>> Date: Fri, 27 Jun 2014 02:35:54 -0700
>> Subject: Re: [R] regular expression help
>> To: dwinsemius at comcast.net
>> CC: baccts at hotmail.com; r-help at r-project.org
>>
>> You can use parentheses to factor out the common string in David's
>> pattern, as in
>> grep(value=TRUE, "(^|//|[[:space:]]+)AARSD1($|//|[[:space:]]+)", test)
>>
>> (By 'whitespace' I could not tell if you meant any amount of
>> whitespace or a single
>> whitespace character. I use '+' to match one or more whitespace characters.)
>>
>> Bill Dunlap
>> TIBCO Software
>> wdunlap tibco.com
>>
>>
>> On Thu, Jun 26, 2014 at 10:12 PM, David Winsemius
>> <dwinsemius at comcast.net> wrote:
>>>
>>> On Jun 26, 2014, at 6:11 PM, C Lin wrote:
>>>
>>>> Hi Duncan,
>>>>
>>>> Thanks for trying to help. Sorry for not being clear.
>>>> The string I'd like to get is 'AARSD1'
>>>> It can be followed or preceded by white space or // or nothing
>>>>
>>>> so, from test <- c('AARSD11','AARSD1-','AARSD1//','AARSD1 //','//AARSD1','AARSD1');
>>>>
>>>> I want to match only 'AARSD1//','AARSD1 //','//AARSD1','AARSD1'
>>>
>>> Perhaps you want jsut
>>>
>>> grepl('^AARSD1//$|^AARSD1 //$|^//AARSD1$|^AARSD1', test)
>>>
>>>> grepl('^AARSD1//$|^AARSD1 //$|^//AARSD1$|^AARSD1$', test)
>>> [1] FALSE FALSE TRUE TRUE TRUE TRUE
>>>
>>> --
>>> David.
>>>
>>>>
>>>
>>>> Thanks,
>>>> Lin
>>>>
>>>> ----------------------------------------
>>>>> From: dulcalma at bigpond.com
>>>>> To: baccts at hotmail.com; r-help at r-project.org
>>>>> Subject: RE: [R] regular expression help
>>>>> Date: Fri, 27 Jun 2014 10:59:29 +1000
>>>>>
>>>>> Hi
>>>>>
>>>>> You only have a vector of length 5 and I am not quite sure of the string you
>>>>> are testing
>>>>> so try this
>>>>>
>>>>> grep('[/]*\\<AARSD1\\>[/]*',test)
>>>>>
>>>>> Duncan
>>>>>
>>>>> Duncan Mackay
>>>>> Department of Agronomy and Soil Science
>>>>> University of New England
>>>>> Armidale NSW 2351
>>>>> Email: home: mackay at northnet.com.au
>>>>>
>>>>> -----Original Message-----
>>>>> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On
>>>>> Behalf Of C Lin
>>>>> Sent: Friday, 27 June 2014 10:05
>>>>> To: r-help at r-project.org
>>>>> Subject: [R] regular expression help
>>>>>
>>>>> Dear R users,
>>>>>
>>>>> I need to match a string. It can be followed or preceded by whitespace or //
>>>>> or nothing.
>>>>> How do I code it in R?
>>>>>
>>>>> For example:
>>>>> test <- c('AARSD11','AARSD1-','AARSD1//','AARSD1 //','//AARSD1');
>>>>> grep('AARSD1(\\s*//*)',test);
>>>>>
>>>>> should return 3,4,5 and 6.
>>>>>
>>>>
>>>
>>>
>>> David Winsemius
>>> Alameda, CA, USA
>>>
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>