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Petr PIKAL

2009-Jul-29 13:10 UTC

[R] regexpr virtue

Hi all

I have got something like that (actually those are column names)

[51] "X19.2.300b...80"          "X19.2.400v...80"
"X19.2.400b...80"
"X19.2.300v...90"          "X19.2.300b...90" 
[56] "X19.2.400v...90"          "X19.2..400b..90"
"X19.2.300v...100"
"X19.2.300b...100"         "X19.2.400v...100" 

in character vector. I would like to get last n figures from this 
character vector but my regexpr unerstanding is inferior and I did not 
succeed. 
Please, is there anybody who can extract those n digits from end of each 
character string? If there were only 2 digits I could use substr but there 
can be one, two or three digits.

I tried several variations of

gsub("0:9$", "\\1" ,names(foto)[10])

but either got whole string or an error.

Best regards
Petr

Gabor Grothendieck

2009-Jul-29 13:20 UTC

head link

[R] regexpr virtue

Here are a couple of possibilities:

sub(".*\\.", "", s)

library(gsubfn)
strapply(s, "[0-9]*$", simplify = c)



On Wed, Jul 29, 2009 at 9:10 AM, Petr PIKAL<petr.pikal at precheza.cz>
wrote:> Hi all
>
> I have got something like that (actually those are column names)
>
> [51] "X19.2.300b...80" ? ? ? ? ?"X19.2.400v...80"
"X19.2.400b...80"
> "X19.2.300v...90" ? ? ? ? ?"X19.2.300b...90"
> [56] "X19.2.400v...90" ? ? ? ? ?"X19.2..400b..90"
"X19.2.300v...100"
> "X19.2.300b...100" ? ? ? ? "X19.2.400v...100"
>
> in character vector. I would like to get last n figures from this
> character vector but my regexpr unerstanding is inferior and I did not
> succeed.
> Please, is there anybody who can extract those n digits from end of each
> character string? If there were only 2 digits I could use substr but there
> can be one, two or three digits.
>
> I tried several variations of
>
> gsub("0:9$", "\\1" ,names(foto)[10])
>
> but either got whole string or an error.
>
> Best regards
> Petr
>
> ______________________________________________
> R-help at 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.
>

Petr PIKAL

2009-Jul-29 13:32 UTC

head link

[R] regexpr virtue

Thanks

If somebody does not come with more elaborated solution I will adapt 
yours. After strsplit I can get not only 3 but several chunks. If the last 
chunk is every time the one I need then

sapply(strsplit(names(foto),"\\..."), length)
 [1] 2 6 6 6 6 5 5 6 5 3 3 3 3 3 3 3 3 3 3 4 3 3 4 4 3 3 3 3 4 3 3 3 3 3 3 
3 3 3 3 3 3 3 3 3 3 3 3 3 4 3 3 3 3 3 3 3 4 3 3 3 3 3 3 4 4 3 4 3
3>gives me number of chunks which I can use for  selection.

Best regards




Jorge Ivan Velez <jorgeivanvelez at gmail.com> napsal dne 29.07.2009 
15:18:33:
> Dear Petr,
> 
> How about this strsplit()ing them up?
> 
> > x
> [1] "X19.2.400v...80"
> > strsplit(x,"\\...")[[1]][3]
> [1] "80"
> 
> HTH,
> 
> Jorge
> 
> On Wed, Jul 29, 2009 at 9:10 AM, Petr PIKAL <petr.pikal at
precheza.cz>
wrote:> Hi all
> 
> I have got something like that (actually those are column names)
> 
> [51] "X19.2.300b...80"          "X19.2.400v...80"
"X19.2.400b...80"
> "X19.2.300v...90"          "X19.2.300b...90"
> [56] "X19.2.400v...90"          "X19.2..400b..90"
"X19.2.300v...100"
> "X19.2.300b...100"         "X19.2.400v...100"
> 
> in character vector. I would like to get last n figures from this
> character vector but my regexpr unerstanding is inferior and I did not
> succeed.
> Please, is there anybody who can extract those n digits from end of each
> character string? If there were only 2 digits I could use substr but 
there> can be one, two or three digits.
> 
> I tried several variations of
> 
> gsub("0:9$", "\\1" ,names(foto)[10])
> 
> but either got whole string or an error.
> 
> Best regards
> Petr
> 
> ______________________________________________
> R-help at 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.

Petr PIKAL

2009-Jul-29 13:43 UTC

head link

[R] regexpr virtue

Thank you

Gabor Grothendieck <ggrothendieck at gmail.com> napsal dne 29.07.2009 
15:20:40:
> Here are a couple of possibilities:
> 
> sub(".*\\.", "", s)
This seems to be the target. Can you be so kind and translate for me what 
it really does?

".* matches several dots?
\\. what is this?

I thought sub finds a match and replaces "replacement" in a string.
But
from this solution it seems that the command replaces all characters in a 
string with empty string and leave only value after three or two dots? Am 
I right?

Best regards
Petr


> 
> library(gsubfn)
> strapply(s, "[0-9]*$", simplify = c)
> 
> 
> 
> On Wed, Jul 29, 2009 at 9:10 AM, Petr PIKAL<petr.pikal at
precheza.cz>
wrote:> > Hi all
> >
> > I have got something like that (actually those are column names)
> >
> > [51] "X19.2.300b...80"          "X19.2.400v...80"
"X19.2.400b...80"
> > "X19.2.300v...90"          "X19.2.300b...90"
> > [56] "X19.2.400v...90"          "X19.2..400b..90"
"X19.2.300v...100"
> > "X19.2.300b...100"         "X19.2.400v...100"
> >
> > in character vector. I would like to get last n figures from this
> > character vector but my regexpr unerstanding is inferior and I did not
> > succeed.
> > Please, is there anybody who can extract those n digits from end of 
each> > character string? If there were only 2 digits I could use substr but 
there> > can be one, two or three digits.
> >
> > I tried several variations of
> >
> > gsub("0:9$", "\\1" ,names(foto)[10])
> >
> > but either got whole string or an error.
> >
> > Best regards
> > Petr
> >
> > ______________________________________________
> > R-help at 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.
> >

Gabor Grothendieck

2009-Jul-29 16:06 UTC

head link

[R] regexpr virtue

dot means any character and * repeats it for as many times
as possible so it replaces eveything (.*) up to the last
dot (\\.) with nothing.

On Wed, Jul 29, 2009 at 9:43 AM, Petr PIKAL<petr.pikal at precheza.cz>
wrote:> Thank you
>
> Gabor Grothendieck <ggrothendieck at gmail.com> napsal dne 29.07.2009
> 15:20:40:
>
>> Here are a couple of possibilities:
>>
>> sub(".*\\.", "", s)
>
> This seems to be the target. Can you be so kind and translate for me what
> it really does?
>
> ".* matches several dots?
> \\. what is this?
>
> I thought sub finds a match and replaces "replacement" in a
string. But
> from this solution it seems that the command replaces all characters in a
> string with empty string and leave only value after three or two dots? Am
> I right?
>
> Best regards
> Petr
>
>
>
>>
>> library(gsubfn)
>> strapply(s, "[0-9]*$", simplify = c)
>>
>>
>>
>> On Wed, Jul 29, 2009 at 9:10 AM, Petr PIKAL<petr.pikal at
precheza.cz>
> wrote:
>> > Hi all
>> >
>> > I have got something like that (actually those are column names)
>> >
>> > [51] "X19.2.300b...80" ? ? ? ?
?"X19.2.400v...80" "X19.2.400b...80"
>> > "X19.2.300v...90" ? ? ? ? ?"X19.2.300b...90"
>> > [56] "X19.2.400v...90" ? ? ? ?
?"X19.2..400b..90" "X19.2.300v...100"
>> > "X19.2.300b...100" ? ? ? ? "X19.2.400v...100"
>> >
>> > in character vector. I would like to get last n figures from this
>> > character vector but my regexpr unerstanding is inferior and I did
not
>> > succeed.
>> > Please, is there anybody who can extract those n digits from end
of
> each
>> > character string? If there were only 2 digits I could use substr
but
> there
>> > can be one, two or three digits.
>> >
>> > I tried several variations of
>> >
>> > gsub("0:9$", "\\1" ,names(foto)[10])
>> >
>> > but either got whole string or an error.
>> >
>> > Best regards
>> > Petr
>> >
>> > ______________________________________________
>> > R-help at 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.
>> >
>
>

Chuck Taylor

2009-Jul-29 17:45 UTC

head link

[R] regexpr virtue

Petr,

Here is a different approach. It, in effect, works from the end of the
string backwards, rather than from the beginning of the string forwards.

   substring(x, regexpr("[0-9]+$", x))

The regular expression "[0-9]+$" finds a string of 1 or more
("+")
digits ("[0-9]") followed by the end of the line ("$"). The
regexpr()
function returns the position in the string x where that regular
expression begins. Feed that to substring() and you get the desired
result. Both substring() and regexpr() work on vectors of strings.

Best regards,
Chuck Taylor
TIBCO Spotfire Seattle


-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On Behalf Of Petr PIKAL
Sent: Wednesday, July 29, 2009 6:10 AM
To: r-help at stat.math.ethz.ch
Subject: [R] regexpr virtue

Hi all

I have got something like that (actually those are column names)

[51] "X19.2.300b...80"          "X19.2.400v...80"
"X19.2.400b...80"
"X19.2.300v...90"          "X19.2.300b...90" 
[56] "X19.2.400v...90"          "X19.2..400b..90"
"X19.2.300v...100"
"X19.2.300b...100"         "X19.2.400v...100" 

in character vector. I would like to get last n figures from this 
character vector but my regexpr unerstanding is inferior and I did not 
succeed. 
Please, is there anybody who can extract those n digits from end of each

character string? If there were only 2 digits I could use substr but
there 
can be one, two or three digits.

...

Best regards
Petr

Petr PIKAL

2009-Jul-30 06:29 UTC

head link

[R] regexpr virtue

Many thanks to you and all others for solutions together with regular 
expressions insights.

Petr

"Chuck Taylor" <ctaylor at tibco.com> napsal dne 29.07.2009
19:45:10:
> Petr,
> 
> Here is a different approach. It, in effect, works from the end of the
> string backwards, rather than from the beginning of the string forwards.
> 
>    substring(x, regexpr("[0-9]+$", x))
> 
> The regular expression "[0-9]+$" finds a string of 1 or more
("+")
> digits ("[0-9]") followed by the end of the line ("$").
The regexpr()
> function returns the position in the string x where that regular
> expression begins. Feed that to substring() and you get the desired
> result. Both substring() and regexpr() work on vectors of strings.
> 
> Best regards,
> Chuck Taylor
> TIBCO Spotfire Seattle
> 
> 
> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at
r-project.org]
> On Behalf Of Petr PIKAL
> Sent: Wednesday, July 29, 2009 6:10 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] regexpr virtue
> 
> Hi all
> 
> I have got something like that (actually those are column names)
> 
> [51] "X19.2.300b...80"          "X19.2.400v...80"
"X19.2.400b...80"
> "X19.2.300v...90"          "X19.2.300b...90" 
> [56] "X19.2.400v...90"          "X19.2..400b..90"
"X19.2.300v...100"
> "X19.2.300b...100"         "X19.2.400v...100" 
> 
> in character vector. I would like to get last n figures from this 
> character vector but my regexpr unerstanding is inferior and I did not 
> succeed. 
> Please, is there anybody who can extract those n digits from end of each
> 
> character string? If there were only 2 digits I could use substr but
> there 
> can be one, two or three digits.
> 
> ...
> 
> Best regards
> Petr

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