[R] Adding error bars to a trellis barchart display

[Chris Bergstresser]

Hi all --

   I'm using trellis to generate bar charts, but there's no built-in
function to generate error bars or confidence intervals, as far as I
can tell.  I assumed I could just write my own panel function to add
them, so I searched the archive, and found a posting from the author
of the package stating "... placing multiple bars side by side needs
specialized calculations, which are done within panel.barchart. To add
bars to these, you will need to reproduce those calculations."
   Just so I'm clear on this -- there's no capacity to add bars to the
plot, nor to find out the coordinates of the bars in the graphs
themselves.  If you want them, you have to completely rewrite
panel.barchart.  Is this correct?  Are there really so few people
using error bars with bar charts?

-- Chris