Removing "+" and "?" signs

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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 "
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)
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.

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

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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
And if you want to replace both "+" and "?", here is a suggestion:

x <- "asdf+,jkl?"
gsub("[?]|[+]", "", x)
# [1] "asdf,jkl"
Once you're into character classes ([....]), you might as well go all 
the way:

 > gsub("[?+]", "", x)
[1] "asdf,jkl"
O__  ---- Peter Dalgaard             ?ster Farimagsgade 5, Entr.B
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