[R] Lattice: problem using panel.superpose and panel.groups

[Michael Braun]

Hi.  I'm embarking on my first attempt at creating my own panel  
function for lattice graphics, and despite all of my online research  
and pouring through the documentation, I cannot figure out how to  
solve my particular problem.  Hopefully, a generous fellow R user can  
help.

I have some data that is split into two groups:  some "actual" data,  
and some simulated data, generated from several different models.  The  
actual data come from two different datasets (calibration and  
holdout), and the simulations were calibrated on each data set under  
the various models.

What I want to do is create a boxplot on the simulated data, and  
superimpose a line representing the actual data.  This plot would  
condition on dataset and model.  While the simulated data various  
across model and dataset, the actual data varies only across dataset  
and is common for all models.

My approach was to use panel.superpose, and create a panel function  
that, depending on the group.number, calls either panel.bwplot or  
panel.lines.  Like this:

panel.custom.plot <- function (..., group.number) {

	if (group.number == 1) {
		panel.bwplot(...)
	} else {
		panel.lines(...)
	}
}

obj <- bwplot(p ~ as.factor(count) | dataset + model, data = data.frame,
	panel = panel.superpose,
	groups = group,
        panel.groups = panel.custom.plot
}


When I do this, I see the bwplot, but I cannot see the lines.  It is  
as though the data isn't being passed through.

Can someone help me get started with this, and instruct me a little  
bit more on how arguments are passed from trellis functions to the  
panel functions?

I did consider a second approach, where I don't use panel.superpose or  
groups at all, but pass the actual.calib and actual.hold datasets as  
parameters to a panel function.  This panel function would call  
panel.bwplot, and then, depending on the value of dataset, add lines  
for either actual.calib or actual.hold.  But I do not know how to let  
the panel function know what level of a conditioning variable is being  
plotted in a particular panel.

Thanks in advance for any help you can provide,

Michael



Michael Braun
Homer A. Burnell Career Development Professor
	and Assistant Professor of Management Science (Marketing Group)
MIT Sloan School of Management
One Amherst St., E40-169
Cambridge, MA 02139
(617) 253-3436
braunm at mit.edu