[R] Is there a better way to parse strings than this?

[Chris Howden]

Thanks for the explanation,

I think I understand it now. So to paraphrase all your explanations

To match "." in a regular expression then the string "\.\.\." needs to be
passed to it. This tells it to escape the special meaning of ".". But in
order to get the \ into the string being passed to the function I also
need to escape its special meaning, so I need to use "\\.\\.\\."



Chris Howden
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-----Original Message-----
From: h.wickham at gmail.com [mailto:h.wickham at gmail.com] On Behalf Of Hadley
Wickham
Sent: Friday, 15 April 2011 11:07 AM
To: Chris Howden
Cc: r-help at r-project.org
Subject: Re: [R] Is there a better way to parse strings than this?

> I was trying strsplit(string,"\.\.\.") as per the suggestion in Venables
> and Ripleys book to "(use '\.' to match '.')", which is in the Regular
> expressions section.
>
> I noticed that in the suggestions sent to me people used:
> strsplit(test,"\\.\\.\\.")
>
>
> Could anyone please explain why I should have used "\\.\\.\\." rather
than
> "\.\.\."?

Basically,

 * you want to match .
 * so the regular expression you need is \.
 * and the way you represent that in a string in R is \\.

Hadley

-- 
Assistant Professor / Dobelman Family Junior Chair
Department of Statistics / Rice University
http://had.co.nz/