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'?' is a metacharacter in a regular expression. You have to escape it:> x <- "asdf+,jkl?" > > gsub("?", " ", x)Error in gsub("?", " ", x) : invalid regular expression '?' In addition: Warning message: In gsub("?", " ", x) : regcomp error: 'Invalid preceding regular expression'> # escape it > gsub("\\?", " ", x)[1] "asdf+,jkl " On Sun, Nov 22, 2009 at 6:01 PM, Steven Kang <stochastickang at gmail.com> wrote:> Hi all, > > > I get an error message when trying to replace *+* or *?* signs (with empty > space) from a string. > > x <- "asdf+,jkl?" > > gsub("?", " ", x) > > > Error message: > > Error in > gsub("?", " ", x) : > ?invalid regular expression '?' > In addition: Warning message: > In gsub("?", " ", x) : > ?regcomp error: ?'Invalid preceding regular expression' > > Your expertise in resolving this issue would be appreciated. > > Thanks. > > > > Steven > > ? ? ? ?[[alternative HTML version deleted]] > > ______________________________________________ > 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. >-- Jim Holtman Cincinnati, OH +1 513 646 9390 What is the problem that you are trying to solve?
Try this:
gsub("[?]", " ", x)
On Mon, Nov 23, 2009 at 7:01 AM, Steven Kang <stochastickang at gmail.com>
wrote:> Hi all,
>
>
> I get an error message when trying to replace *+* or *?* signs (with empty
> space) from a string.
>
> x <- "asdf+,jkl?"
>
> gsub("?", " ", x)
>
>
> Error message:
>
> Error in
> gsub("?", " ", x) :
> ?invalid regular expression '?'
> In addition: Warning message:
> In gsub("?", " ", x) :
> ?regcomp error: ?'Invalid preceding regular expression'
>
> Your expertise in resolving this issue would be appreciated.
>
> Thanks.
>
>
>
> Steven
>
> ? ? ? ?[[alternative HTML version deleted]]
>
> ______________________________________________
> 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.
>
On 23/11/2009, at 12:01 PM, Steven Kang wrote:> Hi all, > > > I get an error message when trying to replace *+* or *?* signs > (with empty > space) from a string. > > x <- "asdf+,jkl?" > > gsub("?", " ", x) > > > Error message: > > Error in > gsub("?", " ", x) : > invalid regular expression '?' > In addition: Warning message: > In gsub("?", " ", x) : > regcomp error: 'Invalid preceding regular expression' > > Your expertise in resolving this issue would be appreciated.(a) That's funny. I don't get an error message when I try your example. I get [1] " a s d f + , j k l ? " Of course that's not what you want, though. (b) You need to escape the question mark: > gsub("\\?", " ", x) yields [1] "asdf+,jkl " which I think *is* what you want. cheers, Rolf Turner ###################################################################### Attention:\ This e-mail message is privileged and confid...{{dropped:9}}
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On Nov 22, 2009, at 6:01 PM, Steven Kang wrote:> Hi all, > > > I get an error message when trying to replace *+* or *?* signs (with > empty > space) from a string. > > x <- "asdf+,jkl?" > > gsub("?", " ", x)Since both ? and + are special regex characters, to do both the substitutions at once you need to use double backslashes and an <or> > gsub("\\?|\\+", " ", x) [1] "asdf ,jkl " -- David> > > Error message: > > Error in > gsub("?", " ", x) : > invalid regular expression '?' > In addition: Warning message: > In gsub("?", " ", x) : > regcomp error: 'Invalid preceding regular expression' > > Your expertise in resolving this issue would be appreciated. > > Thanks. > > > > Steven > > [[alternative HTML version deleted]] > > ______________________________________________ > 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.David Winsemius, MD Heritage Laboratories West Hartford, CT