[R] Overlaying lattice graphs (continued)

From: Sébastien <pomchip_at_free.fr>
Date: Wed, 20 Jun 2007 23:57:13 -0400

Dear R Users,

I recently posted an email on this list about the use of data.frame and overlaying multiple plots. Deepayan kindly indicated to me the panel.superposition command which worked perfectly in the context of the example I gave.
I'd like to go a little bit further on this topic using a more complex dataset structure (actually the one I want to work on).


      Plot Model Individuals Time Observed Predicted

1    1        A           1                  0.05         
10                    10.2
2    1        A           1                  0.10         
20                    19.5
10  1        B           1                  0.05         10            
11  1        B           1                  0.10         20            


There are p "levels" in mydata$Plot, m in mydata$Model, n in mydata$Individuals and t in mydata$Time (Note that I probably use the word levels improperly as all columns are not factors). Basically, this dataset summarizes the t measurements obtained in n individuals as well as the predicted values from m different modeling approaches (applied to all individuals). Therefore, the observations are repeated m times in the Observed columns, while the predictions appears only once for a given model an a given individual.

What I want to write is a R batch file creating a Trellis graph, where each panel corresponds to one individual and contains the observations (as scatterplot) plus the predicted values for all models (as lines of different colors)... $Plot is just a token: it might be used to not overload graphs in case there are too many tested models. The fun part is that the values of p, m, n and t might vary from one dataset to the other, so everything has to be coded dynamically.

For the plotting part I was thinking about having a loop in my code containing something like that:

for (i in 1:nlevels(mydata$Model)) {

subdata<-subset(mydata,mydata$Model=level(mydata$Model)[i]) xyplot(subset(Observed + Predicted ~ Time | Individuals, data = subdata) #plus additionnal formatting code


Unfortunately, this code simply creates a new Trellis plot instead of adding the model one by one on the panels. Any idea or link to a useful command will wellcome.


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