[R] How to quieten axis() for Sweave: avoid echoing NULL?

[Andrew Robinson]

Dear R-community,

I'm using Sweave to produce reports.  The reports require the "axis"
command.  When I run axis the program returns NULL as well as creating
the axis.  

> plot(1:4, rnorm(4), axes=FALSE)
> axis(1, 1:4, LETTERS[1:4])
NULL
>

So, my Sweave tex files have 

\begin{Schunk}
\begin{Soutput}
NULL
\end{Soutput}
\end{Schunk}

in front of each graphic that requires axis.  I can easily find them
and remove them, but I was wondering: is it something I can avoid?  Or
am I doing something foolish and obvious?

Thanks for any assistance,

Andrew
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