[R] Sweave and backslashes

[Frank E Harrell Jr]

cls59 wrote:
> Hello Everyone,
> 
> I am an avid Sweave user and I am trying to pretty print floating point
> numbers for latex output. For example in my document, I would like:
> 
> 4.2\cdot 10^-{8}
> 
> Instead of:
> 
> 4.2e-08
> 
> The Hmisc package has a nice function for doing this- but Hmisc has a ton of
> dependencies and has proved very unportable to the various machines I work
> on. So, I set out to write my own function that just uses basic R commands,

Please name the dependencies that are bothering you.
Frank Harrell

> it looks like this:
> 
> latexNum <- function (x,dig=4,sci=T) 
> {
>     x <- format(x,digits=dig,scientific=sci)
> 		
>          x <- gsub("e\\+00","",x)
>          x <- gsub("e\\-0([0-9]*)","\\\\cdot 10^{-\\1}",x)
> 	 x <- gsub("e\\-([0-9]*)","\\\\cdot 10^{-\\1}",x)
> 	 x <- gsub("e\\+0([0-9]*)","\\\\cdot 10^{\\1}",x)
> 	 x <- gsub("e\\+([0-9]*)","\\\\cdot 10^{\\1}",x)
>          
>         return(x)
> }
> 
> Everything works nicely, if I type
> 
>> latexNum(4*10^-3)
> 
> I get
> 
> [1] "4\\cdot10^{-3}"
> 
> And the following:
> 
>> cat(latexNum(4*10^-3))
> 
> Produces:
> 
> 4\cdot10^{-3}
> 
> However the following in a .Rnw file:
> 
> $\Sexpr{latexNum(4*10^-3)}$\\
> 
> Only produces this in the .tex output file:
> 
> $4cdot 10^{-3}$\\
> 
> No amount of extra backslashing seems to help. Any idea why my escapes are
> not being respected?
> 
> -----
> Charlie Sharpsteen
> Undergraduate
> Environmental Resources Engineering
> Humboldt State University


-- 
Frank E Harrell Jr   Professor and Chair           School of Medicine
                      Department of Biostatistics   Vanderbilt University