Try adding perl = TRUE On Sun, Jul 6, 2008 at 5:17 PM, Duncan Murdoch <[EMAIL PROTECTED]> wrote: > I'm trying to write a gsub() call that takes a string and escapes all the > unescaped quote marks in it. So the string > > \" > > would be left unchanged, but > > \\" > > would be changed to > > \\\" > > because the double backslash doesn't act as an escape for the quote, the > first just escapes the second. I have the usual problems of writing regular > expressions involving backslashes which make everything I write completely > unreadable, so I'm going to change the problem for this post: I will define > E to be the escape character, and q to be the quote; the gsub() call would > leave > > Eq > > unchanged, but would change > > EEq > > to EEEq, etc. > > The expression I have come up with after this change is > > gsub( "((^|[^E])(EE)*)q", "\\1Eq", x) > > i.e. "(start of line, or non-escape, followed by an even number of escapes), > all of which we call expression 1, followed by a quote, is replaced by > expression 1 followed by an escape and a quote". > > This works sometimes, but not always: > >> gsub( "((^|[^E])(EE)*)q", "\\1Eq", "Eq") > [1] "Eq" >> gsub( "((^|[^E])(EE)*)q", "\\1Eq", "EEq") > [1] "EEEq" >> gsub( "((^|[^E])(EE)*)q", "\\1Eq", "qaq") > [1] "EqaEq" >> gsub( "((^|[^E])(EE)*)q", "\\1Eq", "qq") > [1] "qEq" > > Notice that in the final example, the first quote doesn't get escaped. Why > not???? > > Duncan Murdoch > > ______________________________________________ > R-help@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. >
______________________________________________ R-help@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.
