[R] help with xyplot

[Ronaldo Reis Jr.]

Hi, 
 
I make a graphic using xyplot, it is very good. 
 
xyplot((ocorrencia/isca)~frag|especie) 
 
But I need to plot a curve for each especie's plot. 
 
I try to use panel.abline and others panel., but I dont succeed. 
 
I need to plot the function exp(a+b*x+c*x^2)/1+exp(a+b*x+c*x^2), a b and c 
are different for each especie.  
 
Normally I use the curve function to add a curve in a points graphics, but it 
dont work with xyplot. 
 
Anybody have any idea? 
 
Thanks 
Ronaldo 
 
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Insecta - Entomologia
Departamento de Biologia Animal
Universidade Federal de Viçosa