[R] Adding error bars to a trellis barchart display

[Deepayan Sarkar]

On 5/13/06, Chris Bergstresser <chris at subtlety.com> wrote:
> 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?

I would hope so, since bar charts with error bars are horrible things,
in my opinion. Lattice comes with an example of (standard) confidence
intervals (new in R 2.3.0) that can be accessed by running

library(lattice)
demo(intervals)

The Hmisc package also has high level interfaces that support
confidence intervals (I'm not familiar with the details).

-Deepayan