[R] Sweave: printing an underscore in the output from an R command

[David Epstein]

Dear Thierry,

Your suggestion doesn't work on my version of R. Here's what I get
> gsub("_", "\_", print(version$platform)
Error: '\_' is an unrecognized escape in character string starting ""\_"
> print(gsub("_", "\_", version$platform))
Error: '\_' is an unrecognized escape in character string starting ""\_"

> sub("_", "\\_", version$platform)
[1] "x86_64-apple-darwin10.8.0"
Sweave does not evaluate this expression when \Sexpr is applied and a tex error results

> sub("_", "\\\_", version$platform)
Error: '\_' is an unrecognized escape in character string starting ""\\\_"
Error message from R

> sub("_", "\\\\_", version$platform)
[1] "x86\\_64-apple-darwin10.8.0"
R evaluates this. However, the above examples indicate a deficiency/possible bug in the command sub, because sub does not seem to be able to output an expression with a single backslash.

I tried the previous version as follows in my .Rnw document
\Sexpr{print(sub("_", "\\\\_", version$platform))}
When Sweave is run, this expression is evaluated to illegal LaTeX

David.




On 2 Sep 2013, at 16:47, ONKELINX, Thierry wrote:

> You have to escape the underscore
> 
> \Sexpr{gsub("_", "\_", print(version$platform))}
> 
> Best regards,
> 
> Thierry
> 
> ________________________________________
> Van: r-help-bounces at r-project.org [r-help-bounces at r-project.org] namens David Epstein [David.Epstein at warwick.ac.uk]
> Verzonden: maandag 2 september 2013 17:38
> Aan: r-help at r-project.org
> Onderwerp: [R] Sweave: printing an underscore in the output from an R command
> 
> I am working with Sweave and would like to print out into my latex document the result of the R command
> version$platform
> So what I first tried in my .Rnw document was \Sexpr{print(version$platform)}.
> 
> However, the output from this command is the string "x86_64-apple-darwin10.8.0" (without the quotes). This contains an underscore, which is a special character in tex and so I get an error message from latex.
> 
> I can get round this by using sub to replace underscore with a space, but I would like to know how to print the underscore if I really wanted to do so.
> 
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