R help - Nov 2004 - I: a coloured band within each panel of a lattice bwplot

Hi all,
I would like to add to each panel of a bwplot a coloured central band,
centered on the mean of the values, being its width +- 2% of the mean
itself.

I know how to add lines, i.e. something like

bwplot(X ~ Y|FACTOR
       data=my.df,
       panel= function(x, y){
         panel.bwplot(x, y)
         panel.abline(v = mean(x, na.rm = T) - mean(x, na.rm = T) * 0.02
         panel.abline(v = mean(x, na.rm = T) + mean(x, na.rm = T) * 0.02
       })

but I cannot figure out how to shade the region included between the two
lines.

Is it possible, or I'm pretending too much?

Thanks to all.

Ottorino-Luca Pantani, Universit?? di Firenze
Dip. Scienza del Suolo e Nutrizione della Pianta

On Friday 05 November 2004 05:05, 8rino-Luca Pantani
wrote:
> Hi all,
> I would like to add to each panel of a bwplot a coloured central
> band, centered on the mean of the values, being its width +- 2% of
> the mean itself.
>
> I know how to add lines, i.e. something like
>
> bwplot(X ~ Y|FACTOR
>        data=my.df,
>        panel= function(x, y){
>          panel.bwplot(x, y)
>          panel.abline(v = mean(x, na.rm = T) - mean(x, na.rm = T) *
> 0.02 panel.abline(v = mean(x, na.rm = T) + mean(x, na.rm = T) * 0.02
> })
>
> but I cannot figure out how to shade the region included between the
> two lines.
Generally speaking, you want to draw a polygon . There is no lattice 
wrapper for the 'grid.polygon' function, so you will have to use it 
directly. Check out 
> library(grid)
> help(grid.polygon)
For this simpler case though, 'grid.rect' should be sufficient, e.g.

       panel= function(x, y){
           m <- mean(x, na.rm = T)
           grid.rect(x = unit(m, "native"),
                     w = unit(m * 0.04, "native"),
                     gp = gpar(fill = "lightgrey", col =
"transparent"))
           panel.bwplot(x, y)
       }

Make sure to do a 'library(grid)' before this.

Deepayan