R help - Jul 2008 - Backslash in sub pattern?

Dear guRus,

I am trying to replace "~" by "$\sim$" for TeX. However, I
can't get the
backslash to work. I would like to turn "DV~IV" into
"DV$\sim$IV".

sub("~","$\sim$","DV~IV") =>
"DV$sim$IV"
sub("~","$\\sim$","DV~IV") =>
"DV$sim$IV"
sub("~","$\\\sim$","DV~IV") =>
"DV$sim$IV"
sub("~","$\\\\sim$","DV~IV") =>
"DV$\\sim$IV"

Alternatives 1 and 3 also yield warnings about unknown escape sequences 
(no surprise there). I have been unsuccessfully searching the archives. 
sessionInfo below.

Thank you all for your time!

Best regards
Stephan


 > sessionInfo()
R version 2.7.1 (2008-06-23)
i386-pc-mingw32

locale:
LC_COLLATE=German_Germany.1252;LC_CTYPE=German_Germany.1252;LC_MONETARY=German_Germany.1252;LC_NUMERIC=C;LC_TIME=German_Germany.1252

attached base packages:
[1] stats     graphics  grDevices utils     datasets  tcltk     methods 
   base

other attached packages:
[1] svIDE_0.9-5

loaded via a namespace (and not attached):
[1] svMisc_0.9-5

on 07/14/2008 01:09 PM Stephan Kolassa wrote:
> Dear guRus,
> 
> I am trying to replace "~" by "$\sim$" for TeX.
However, I can't get the
> backslash to work. I would like to turn "DV~IV" into
"DV$\sim$IV".
> 
> sub("~","$\sim$","DV~IV") =>
"DV$sim$IV"
> sub("~","$\\sim$","DV~IV") =>
"DV$sim$IV"
> sub("~","$\\\sim$","DV~IV") =>
"DV$sim$IV"
> sub("~","$\\\\sim$","DV~IV") =>
"DV$\\sim$IV"
> 
> Alternatives 1 and 3 also yield warnings about unknown escape sequences 
> (no surprise there). I have been unsuccessfully searching the archives. 
> sessionInfo below.
> 
> Thank you all for your time!
> 
> Best regards
> Stephan
You want door number 4 because when the double escape is cat()'d to the 
.tex file, you get:

 > cat("DV$\\sim$IV", "\n")
DV$\sim$IV

which is what you want latex to process.

HTH,

Marc Schwartz

Phil:

thanks a lot! However, my original problem[1] remains: in fact, I am 
trying to \Sexpr the result for Sweave, and for some reason Sweave 
regurgitates the \Sexpr command unchanged:

foo.Rnw contains:
\Sexpr{"DV~IV"}
\Sexpr{cat("DV~IV")}
\Sexpr{sub('~','$\\\\sim$',"DV~IV")}
\Sexpr{cat(sub('~','$\\\\sim$',"DV~IV"),"\n")}

After Sweave(foo) the file foo.tex then contains:
\usepackage{Sweave}
DV~IV

\Sexpr{sub('~','$\\\\sim$',"DV~IV")}
\Sexpr{cat(sub('~','$\\\\sim$',"DV~IV"),"\n")}

(yes, with the blank line resulting from \Sexpr{cat("DV~IV")}), and 
LaTeX understandably complains that \Sexpr is not a valid command.

My goal: I would like to use some function bar() so that

str <- "DV~IV"
\Sexpr{bar(str)}

yields after Sweaving

DV$\sim$IV

in the tex file.

Any thoughts?
Stephan


[1] Sorry, I now see that my commented, minimal, self-contained, 
reproducible code was too minimal... I reduced the problem too far. My bad!



Phil Spector schrieb:
> Stephen -
>     Since the print function in R always displays two backslashes
> for a single one, you really need to use cat or nchar to make sure
> that things are working:
> 
>> sub('~','$\\\\sim$',str)
> [1] "ab$\\sim$cd"
>> cat(sub('~','$\\\\sim$',str),"\n")
> ab$\sim$cd
> 
> It's the result of cat that's actually output, not the string that
> R uses to display it.
> 
> 
>                                        - Phil Spector
>                      Statistical Computing Facility
>                      Department of Statistics
>                      UC Berkeley
>                      spector at stat.berkeley.edu
> 
> 
> On Mon, 14 Jul 2008, Stephan Kolassa wrote:
> 
>> Dear guRus,
>>
>> I am trying to replace "~" by "$\sim$" for TeX.
However, I can't get
>> the backslash to work. I would like to turn "DV~IV" into
"DV$\sim$IV".
>>
>> sub("~","$\sim$","DV~IV") =>
"DV$sim$IV"
>> sub("~","$\\sim$","DV~IV") =>
"DV$sim$IV"
>> sub("~","$\\\sim$","DV~IV") =>
"DV$sim$IV"
>> sub("~","$\\\\sim$","DV~IV") =>
"DV$\\sim$IV"
>>
>> Alternatives 1 and 3 also yield warnings about unknown escape 
>> sequences (no surprise there). I have been unsuccessfully searching 
>> the archives. sessionInfo below.
>>
>> Thank you all for your time!
>>
>> Best regards
>> Stephan
>>
>>
>>> sessionInfo()
>> R version 2.7.1 (2008-06-23)
>> i386-pc-mingw32
>>
>> locale:
>>
LC_COLLATE=German_Germany.1252;LC_CTYPE=German_Germany.1252;LC_MONETARY=German_Germany.1252;LC_NUMERIC=C;LC_TIME=German_Germany.1252
>>
>>
>> attached base packages:
>> [1] stats     graphics  grDevices utils     datasets  tcltk     
>> methods base
>>
>> other attached packages:
>> [1] svIDE_0.9-5
>>
>> loaded via a namespace (and not attached):
>> [1] svMisc_0.9-5
>>
>> ______________________________________________
>> 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.
>>
>