R help - May 2012 - Lattice side by side boxplots with average

Given the following example

library(lattice) 
attach(barley)

After a long meandering around the web I managed to get a side by side
boxplots through:

bwplot(yield ~ site, data = barley, groups=year,
       pch = "|", box.width = 1/3,
       auto.key = list(points = FALSE, rectangles = TRUE, space =
"right"),
       panel = panel.superpose,
       panel.groups = function(x, y, ..., group.number) {
         panel.bwplot(x + (group.number-1.5)/3, y, ...)
       }
       )

now, my objective is to superpose the average for each boxplot;

I?ve been learning, again somewhere around the web, that this task has
something to do (obviously) first of all with the calculation of the
averages, i.e. something like:

mean.values <- tapply(y, x, mean)

and then with the superposition of relative average values to the boxplots,
i.e. something like:

panel.points(?, mean.values, ..., pch = 17)

but for some reasons I?m not able to properly combine these code snippets in
a successful way

any help much appreciated, thank you



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On Tue, May 8, 2012 at 9:32 AM, maxbre <mbressan at arpa.veneto.it> wrote:
> and then with the superposition of relative average values to the boxplots,
> i.e. something like:
>
> panel.points(?, mean.values, ..., pch = 17)
Almost. You need to give panel.points the new x, and make sure the
right mean.values go to the right place because the order of tapply
output is not necessarily the same order as y, even though I never
quite understood why myself...
Bottom line, this should it:

bwplot(yield ~ site, data = barley, groups=year,
       pch = "|", box.width = 1/3,
       auto.key = list(points = FALSE, rectangles = TRUE, space =
"right"),
       panel = panel.superpose,
       panel.groups = function(x, y, ..., group.number) {
         panel.bwplot(x + (group.number-1.5)/3, y, ...)
         mean.values <- tapply(y, x, mean)
         panel.points(x + (group.number-1.5)/3, mean.values[x], pch=17)
})

Cheers
>
> but for some reasons I?m not able to properly combine these code snippets
in
> a successful way
>
> any help much appreciated, thank you
>
>
>
> --
> View this message in context:
http://r.789695.n4.nabble.com/Lattice-side-by-side-boxplots-with-average-tp4617831.html
> Sent from the R help mailing list archive at Nabble.com.
>
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