[R] strsplit with invalid regular expression

[Jeff Newmiller]

In R, the source code representation of a special character uses the \ as an escape character to begin a special character sequence. For example, "\n" is a single newline character.

Because backslash has this special meaning, to represent a single backslash character one must escape it: "\\" looks like two backslashes, but in computer memory it is only one character.

R is not the only software that uses the backslash as an escape character: the syntax of regular expressions handled by the regex library also does, but it uses the backslash to SUPPRESS special meaning.

In your first regex you pass a string containing a backslash followed by a left paren, which tells it to treat the ( as a character to be searched for, not a grouping character that defines a substring to "remember" for backreferencing.

In your second regex you tell it that the letter s should be treated as a normal character (which it is anyway), but the ( retains its special meaning that requires a matching ) in the regex.

I suspect that what you wanted was "sin\\(", which gives sin\( to the regex library.
---------------------------------------------------------------------------
Jeff Newmiller                        The     .....       .....  Go Live...
DCN:<jdnewmil at dcn.davis.ca.us>        Basics: ##.#.       ##.#.  Live Go...
                                      Live:   OO#.. Dead: OO#..  Playing
Research Engineer (Solar/Batteries            O.O#.       #.O#.  with
/Software/Embedded Controllers)               .OO#.       .OO#.  rocks...1k
--------------------------------------------------------------------------- 
Sent from my phone. Please excuse my brevity.

Bharat Warule <bwarule at gmail.com> wrote:

>Hi all,
>
>> diff_operator <- "\\("
>> strsplit(cond, diff_operator)
>[[1]]
>[1] "andsin"         "log_angle_1_4)"
>
>> diff_operator <- "\\sin("
>> strsplit(cond, diff_operator)
>Error in strsplit(cond, diff_operator) : 
>  invalid regular expression '\sin(', reason 'Missing ')''
>
>When I am going to split with "(" it’s working fine but when i want use
>"sin(" this is not working.
>I understand that, I am missing something can anybody please point me.
>Thanks for your help.
>
>Thanks,
>Bharat
>
>
>
>-----
>Bharat Warule 
>Pune
>--
>View this message in context:
>http://r.789695.n4.nabble.com/strsplit-with-invalid-regular-expression-tp4648857.html
>Sent from the R help mailing list archive at Nabble.com.
>
>______________________________________________
>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.