[R] How to create a floating bar plot

[Roberto Brunelli]

I would like to create a 'bar' plot with the following look

            -            0         +
-------------------------+----------------------
            oooooooo************
                                    *********
   ooooooooo
                        oo****

where the positive and negative parts of the bar
should have a different color.

Is there any function/package supporting this kind of plot?

Thanks a lot,

Roberto