[R] Rd file--latex {array} help

[William H. Asquith]

I am trying to build the notation for combination as the function 
\code{choose} in a *.Rd file; but it is not working.
To reduce to essence

\deqn{  \left( \begin{array}{c}
            r-1   \\
            n
         \end{array} \right)
      }

I have double checked the latex logic (without \deqn{}) in LaTexIT on 
MacOSX so it seems fine.
I've read the R-ext.pdf and down some searching in the 
archives--stumped.

R CMD Rd2dvi --pdf

renders something like this

( r-1\n )

Advice?
Thanks.

Wil