Thank you. Single backslash version, first thing I tried (I thought) works just fine when I copy and paste, ergo I must have got confused by some stupid typo of mine. Sorry to waste everyone's time over this. (Still, I am probably not the only confused user when it comes to RE handling - I hope the examples posted will be of as much use to others as they are to me.) Simon
> -----Original Message----- > From: Prof Brian Ripley [mailto:[EMAIL PROTECTED] > Sent: 12 August 2003 17:13 > To: Simon Fear > Cc: [EMAIL PROTECTED] > Subject: Re: [R] grep and gsub on backslash and quotes > > > Security Warning: > If you are not sure an attachment is safe to open please contact > Andy on x234. There are 0 attachments with this message. > ________________________________________________________________ > > On Tue, 12 Aug 2003, Simon Fear wrote: > > > The following code works, to gsub single quotes to double quotes: > > > > line <- gsub("'", '"', line) > > > > (that's a single quote within doubles then a double within > singles if > > your > > viewer's font is not good). > > > > But The R Language Manual tells me that > > > > Quotes and other special characters within strings > > are specified using escape sequences: > > \' single quote > > \" double quote > > > > so why is the following wrong: gsub("\\\\'", "\\\\"", line)? That or > any > > other number of backslashes (have tried all up to n=6 just for good > > measure). > > > > BTW is it documented anywhere that you need four > backslashes in an RE > to > > match one in the target, when it is being passed as an argument to > gsub > > or > > grep? > > It's not true, so I hope it is not documented anywhere. You > may need 6, > as in the following from methods(): > > res <- sort(grep(gsub("([.[])", "\\\\\\1", name), an, > value = TRUE)) > > since that is \\ \1 withou tthe space. Each backslash in the target > only > needs to be doubled. > > In your example > > gsub("\'", "\"", line) or even gsub("'", "\"", line) > > is all you need: only R strings need the escape. > > > -- > Brian D. Ripley, [EMAIL PROTECTED] > Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ > University of Oxford, Tel: +44 1865 272861 (self) > 1 South Parks Road, +44 1865 272866 (PA) > Oxford OX1 3TG, UK Fax: +44 1865 272595 > Simon Fear Senior Statistician Syne qua non Ltd Tel: +44 (0) 1379 644449 Fax: +44 (0) 1379 644445 email: [EMAIL PROTECTED] web: http://www.synequanon.com Number of attachments included with this message: 0 This message (and any associated files) is confidential and\...{{dropped}} ______________________________________________ [EMAIL PROTECTED] mailing list https://www.stat.math.ethz.ch/mailman/listinfo/r-help