[R] regular expression help

[Petr PIKAL]

Thank you all for your working solutions


Petr Pikal
petr.pikal at precheza.cz

r-help-bounces at stat.math.ethz.ch napsal dne 18.04.2007 13:26:36:

> A backreference is contained in parentheses and there are no parentheses
> in your regular expression, hence the error message.
> 
> Its probably easiest just to remove all non-letters:
> 
> x <- "45x53yy66"
> gsub("[^[:alpha:]]", "", x) # xyy
> 
> On 4/18/07, Petr PIKAL <petr.pikal at precheza.cz> wrote:
> > Dear all
> >
> > as usual I am again lost in virtues of regular expressions.
> >
> > I have such character vector named vzor:
> >
> > [365] "61A"      "62C/27"   "65A/27"   "66C/29"   "69A/29"   "70C/31"
> > "73A/31"   "74C/33"   "77A/33"   "81A/35"   "82C/37"   "85A/37" 
"86C/39"
> >
> > [378] "89A/39"   "90C/41"   "93A/41"   "94C/43"   "97A/43"   "98C/45"
> > "101A/45"  "102C/47"  "105A/47"  "106C/49"  "109A/49"  "110C/51" 
"113A/51"
> >
> >
> > and I want only letters from it.
> >
> > I tried
> >
> > > gsub("[[:alpha:]]"," \\1",vzor)
> > Error in gsub("[[:alpha:]]", " \\1", vzor) :
> >        invalid backreference 1 in regular expression
> >
> > gsub("[:alpha:]"," \\1",vzor)
> >
> > gives me the same vector
> >
> > There is probably very simple solution to it which I overlooked and
> > examples in help page did not help me to find it.
> >
> > Thank you
> > Best regards
> >
> > Petr Pikal
> > petr.pikal at precheza.cz
> >
> > ______________________________________________
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> > PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
> > and provide commented, minimal, self-contained, reproducible code.
> >
> 
> ______________________________________________
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> PLEASE do read the posting guide 
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.