toupper does not work in sub + regex

Mon, Apr 13, 2009 10:46 AM

The easiest way to do that is to use Gabor's gsubfn package.
There doesn't appear to be a \\<letter> code that means don't convert
the rest of the replacement items to upper or lower case.

You could use other methods to avoid gsubfn.  E.g.,
  > sub("(q_)([a-z])", "\\U\\2", "q_sviRaw",perl=TRUE)
  [1] "SviRaw"

Did not work. 

Thank you!
Richard

-----Original Message-----
From: William Dunlap [mailto:wdunlap at tibco.com] 
Sent: Monday, April 13, 2009 1:17 PM
To: Tan, Richard; r-help at r-project.org
Subject: Re: [R] toupper does not work in sub + regex

You could also use \\U and \\L in the replacement with perl=TRUE.  \\U
"converts the rest of the replacement to upper case" and \\L 
converts to
lowercase. (By "replacement" it means the parts of the 
replacement that
arise from parenthesized subpatterns in the pattern argument, not the
replacement argument itself.)  E.g.,

sub("q_([a-z])[a-zA-Z]*", "\\U\\1\\L", "q_sviRaw", perl=TRUE)

[1] "S"

sub("q_([a-z])([a-zA-Z]*)", "\\U\\1 then \\L\\2", "q_sviRaw",

perl=TRUE)
[1] "S then viraw"

sub("q_([a-z])([a-zA-Z]*)", "\\U\\1 then \\2", "q_sviRaw",

perl=TRUE)
[1] "S then VIRAW"

Bill Dunlap
TIBCO Software Inc - Spotfire Division
wdunlap tibco.com 

----------------------------------------------------------------------
[R] toupper does not work in sub + regex

Gabor Grothendieck ggrothendieck at gmail.com Mon Apr 13 18:26:12 CEST
2009

sub only handles replacement strings, not replacement functions.
Your code is the same as:

sub("q_([a-z])[a-zA-Z]*", '\\1', "q_sviRaw")

since toupper('\\1') has no alphabetics so its just literally 
'\\1' and
the latter is what sub uses.

The gsubfn function in the gsubfn package can deal with replacement
functions:

library(gsubfn)
gsubfn("q_([a-z])[a-zA-Z]*", toupper, "q_sviRaw")

[1] "S"

See the home page: http;//gsubfn.googlecode.com, vignette and 
help page.

On Mon, Apr 13, 2009 at 11:54 AM, Tan, Richard <RTan at panagora.com>
wrote:

Hi, I don't know what I am doing wrong to the toupper does not seem 
working in sub + regex.  The following returns 's' not the

upper class

'S' as I expect:

sub("q_([a-z])[a-zA-Z]*",toupper('\\1'),"q_sviRaw")

Can someone tell me where I did wrong?

Thanks,
Richard

toupper does not work in sub + regex

Thread (3 messages)