[R] Help with regular expressions

[Ulrik Stervbo]

I think I would replace all , with . and subsequently replace all first .
with , using ^\\.

x <- gsub(",", ".", x)
gsub("^\\.", ",", x)

It's not so elegant, but it is easier to understand than backreferences and
complex regex.

Best,
Ulrik

On Tue, 13 Feb 2018, 03:38 Boris Steipe, <boris.steipe at utoronto.ca> wrote:

> You can either use positive lookahead/lookbehind - but support for that is
> a bit flaky. Or write a proper regex, and use
> backreferences to keep what you need.
>
> R > x <- "abc 1,1 ,1 1, x,y 2,3 "
>
> R > gsub("(\\d),(\\d)", "\\1.\\2", x, perl = TRUE)
> [1] "abc 1.1 ,1 1, x,y 2.3 "
>
>
> B.
>
>
>
> > On Feb 12, 2018, at 9:34 PM, Jim Lemon <drjimlemon at gmail.com> wrote:
> >
> > Hi Dennis,
> > How about:
> >
> >
> > # define the two values to search for
> > x<-2
> > y<-3
> > # create your search string and replacement string
> > repstring<-paste(x,y,sep=",")
> > newstring<-paste(x,y,sep=".")
> > # this is the string that you want to change
> > thetastring<-"SIGMA(2,3)"
> > sub(repstring,newstring,thetastring)
> > [1] "SIGMA(2.3)"
> >
> > Use gsub if you want to change multiple values
> >
> > Jim
> >
> > On Tue, Feb 13, 2018 at 1:22 PM, Dennis Fisher <fisher at plessthan.com>
> wrote:
> >> R 3.4.2
> >> OS X
> >>
> >> Colleagues
> >>
> >> I would appreciate some help with regular expressions.
> >>
> >> I have string that looks like:
> >>        " ITERATION              ,THETA1                 ,THETA2
>          ,THETA3                 ,THETA4                 ,THETA5
>      ,THETA6                 ,THETA7                 ,SIGMA(1,1)
>  ,SIGMA(2,1)             ,SIGMA(2,2)”
> >>
> >> In the entries that contain:
> >>        (X,Y)                   # for example, SIGMA(1,1)
> >> I would like to replace the comma with a period, e.g., SIGMA(1.1) but
> NOT the other commas
> >>
> >> The end-result would be:
> >>        " ITERATION              ,THETA1                 ,THETA2
>          ,THETA3                 ,THETA4                 ,THETA5
>      ,THETA6                 ,THETA7                 ,SIGMA(1.1)
>  ,SIGMA(2.1)             ,SIGMA(2.2)”
> >>
> >> Can someone provide the regular expression code to accomplish this?
> >> Thanks.
> >>
> >> Dennis
> >>
> >> Dennis Fisher MD
> >> P < (The "P Less Than" Company)
> >> Phone / Fax: 1-866-PLessThan (1-866-753-7784)
> >> www.PLessThan.com
> >>
> >> ______________________________________________
> >> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> >> 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.
> >
> > ______________________________________________
> > R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> > 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.
>
> ______________________________________________
> R-help at r-project.org mailing list -- To UNSUBSCRIBE and more, see
> 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.
>

	[[alternative HTML version deleted]]