R help - May 2008 - Defining factors for graphical presentations and incorporation of a smoother overlay line

Hello,
I have some photosynthesis data that is grouped by SPECIES and REPLICATION
I have tried to develop a grouped data set with the following:
photo.gd <- groupedData(Photo~PARi|Species, 
 data = photo.frm,  
 labels = list(x = "PPFD (expression(paste)µ mol photons m^-2 s^-1)", 
               y = "Net photosynthetic rate (expression(paste)µ mol
CO[2]m^-2 s^-1)") ,
 units = list(y = "(std temp)")
 )
plot(photo.gd,aspect=1)

How do I add REPLICATION as an ordered factor to the grouped data setup?
How can I incorporate a mean (distance weight least squares) line as part of a
graph for each replicate set.


Thank you, 
Earl Sparkes 

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