[Rd] Problem with formatted xtable in R 2.5.0

[Prof Brian Ripley]

On Fri, 27 Apr 2007, Pfaff, Bernhard Dr. wrote:

> Dear R-Devel subscriber,
>
> I encountered the following problem for tex-formatted table with 
> xtable(). Suppose I do want the following matrix as a table in LaTeX:
>
> library(xtable)
> a11 <- "\\color{green}\\textbf{big green}"
> a21 <- "\\color{red}\\textbf{big red}"
> a12 <- "\\color{green}green"
> a22 <- "\\color{red}red"
> A <- matrix(c(a11, a21, a12, a22), nrow = 2, ncol = 2)
> colnames(A) <- c("big", "normal")
> rownames(A) <- c("green", "red")
> A
> xtable(A, vsep=c('@{\\hspace{0.1cm}}', rep('@{\\hspace{0.4cm}}', 6), '@{\\hspace{0.1cm}}'))
>
> I do get the following output:
>
> % latex table generated in R 2.5.0 by xtable 1.4-3 package
> % Fri Apr 27 13:19:43 2007
> \begin{table}[ht]
> \begin{center}
> \begin{tabular}{rll}
>  \hline
> & big & normal \\
>  \hline
> green & $\backslash$color\{green\}$\backslash$textbf\{big green\} & $\backslash$color\{green\}green \\
>  red & $\backslash$color\{red\}$\backslash$textbf\{big red\} & $\backslash$color\{red\}red \\
>   \hline
> \end{tabular}
> \end{center}
> \end{table}
>
>
> Please, note that the curly braces are prefixed with a backslash and the 
> double backslashes are interpreted as math backslashes. The above code 
> snippet worked fine in R 2.4.1 and I reckon that this behaviour might be 
> due to:
>
> o	There is a warning if \ is used unnecessarily in a string when
> 	being parsed, e.g. "\." where probably "\\." was intended.
> 	("\." is valid, but the same as ".".)  Thanks to Bill Dunlap
> 	for the suggestion.

How can a warning that you are not showing (and I don't see when running 
your code) have anything to do with this?  That change is just to add a 
warning: there is no change in the parsed code.

I get the same behaviour in 2.4.1 with xtable 1.4-3.  Have you 
perhaps updated 'xtable' as well as R and are blaming R for an 'xtable' 
change?  As ?print.xtable says

      From version 1.4-3, all non-numeric columns are sanitized, and all
      LaTeX special characters are sanitised for LaTeX output. See the
      vignette for an example of customising the sanitization.

[...]

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595