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regexpr virtue

6 messages · PIKAL Petr, Gabor Grothendieck, Chuck Taylor

Original
PIKAL Petr
# 
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
# 
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:
PIKAL Petr
# 
Thank you

Gabor Grothendieck <ggrothendieck at gmail.com> napsal dne 29.07.2009 
15:20:40:
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
wrote:
each
there
http://www.R-project.org/posting-guide.html
Gabor Grothendieck
# 
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:
Chuck Taylor
# 
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
PIKAL Petr
# 
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: