panel function mathdensity: How to get the parameters into that??

[Karin <twentestat@yahoo.com>]

Hello,

I am looking for a hint in the following:

I have observations on 'ydata' (relative duration) for several muscles (MUSCLE) 
and during several activities (ACT_2). Now I want to plot histograms of 
ydata with a panel function for each muscle and activity. Next to the histogram 
I want to plot the estimated beta distribution for that panel with 
panel.mathdensity. But how can I get the parameters for the beta distribution 
per panel into the panelfunction (shape1 and shape2)
?

histogram( ~ ydata | MUSCLE*ACT_2,data=temp2,xlab="Relative duration", type = 
"density",
          panel = function(x, ...) {
              panel.histogram(x, ...)
              panel.mathdensity(dmath = dbeta, col = "black",
                                args = list(shape1=??,shape2=???? )))
          } )

Thanks in advance,

Karin Groothuis