[R] structure data

[Antje]

Hello,

I have a quite simple question, I guess. I have a data frame and I would like 
to process the data in several ways.
The processing is dependent on grouping (factors) and the parameter itself. 
Meaning for parameter1 in the df, I would like to calculate the mean and sd 
when grouping by factor1. But parameter2 might be different. I thought of a 
structure like this:

group1
     param1   (mean, sd)
     param2   (sum)

group2
     param1   (mean, sd, median)
     param2   (mean, sd)

I'm not sure how to build up this "processing info" structure. (The processing 
itself will be later based on this structure).
Would you use a list? (matrix and vector are not so flexible for different 
length...)

Can anybody help m with this?

Antje